It must be an AI. There is no way the Real liveoverflow would have ever let this slip, He cut it, he render it, he watch it He uploads it. Multiple occasions where an Actual human would have seen the magical number but not an AI.. For an AI it's just a number. Therefore Liveroverflow has replaced himself with an AI
It feels like it's a special case of DOM Clobbering, right? We are overwriting the names/definitions of defined variables/functions with our payloads so that they get executed when the page's code calls the overwritten function without knowing it.
Nice video explaining the issue. One thing that I think is good to mention is what is the underlying mistake. This makes it a better resource for devs and also for researchers. In my humble opinion this is due to the fact that the person implementing this tried to it's own filtering instead of using the native available functionality and/or standard package. The red flag beeing the specific list of characters used for filtering
I like this as a reoccurring video. It is nice to be able to decipher what someone was referring to. Given everyone has different levels of knowledge, I would give it a 2 thumbs up. Keep ‘em coming!
This is not really JS problems as some people seems to think. Carelessly treating user's input would always lead to big problems. In general when developing FE applications we rarely set any user provided values in any context that could be evaluated like this. Concatenating user's input with code is just bad practice and big no-no. In general, interesting information, but highly theoretical: so many characters are disallowed while double quote still being allowed. I feel IRL, if such case would be allowed, would be either no input cleaning or stricter rules.
Sadly most websites stubbornly develop their own ways of providing rich text display methods instead of using standards, which generally just tends to expose users to exploits... I know that all too well. Been working on the frontend for a while (please kill me)
I have seen a lot of old codebase concatenating user's input with code, it really isn't that bad as long as you know what you are doing. Also in those applications you just can't rewrite the majority of the codebase just to fix a newly discovered XSS. Sorry I lied it was so damn bad that it has become a joke where the filter list just increases day by day. We slapped on a 5000$ IDS and IPS service and everyone pretends like everything is in control but deep inside we all know that the codebase is on fire. I know Robert had told me for a thousand time that concatenating user input with code is bad, but when deadline is chasing off my a** I just can't help but pray and do it anyway, I just want to go home. Sorry Robert, I swear it will be the last time I do it. Amen.
you are absolutely right. thats also almost always my first thought. but i have to throw that thought away for a moment because it gets more interessting if you think about all the existing websites who still could have flaws like this. and its also interesting just to see again how sh*tty and dirty compilcated and entangled javascript can be as a scripting language :D
it kind of is. javascript is dogshit and was made to do simple things when it was created but some clowns said "hold my beer" and other clowns took it seriously, then nodejs happened and embedded webshit posing as fully functional desktop applications known as electron came to be and it's at its worse. Thank God I don't ever was forced to dabble in this cesspool profesionally
Cool, but not one programmer who respects himself will not write such a shit code. I will say more, in order to allow such a vulnerability, you need to try hard
i refuse to create a twitter account, and twitter doesn't allow viewing without a account so. i can't look at the links you posted. at least Tiktok allows you to view stuff without requiring a account. but i hate tiktok
I’ve never seen an actual real world example of a successful XSS or SQL injection attack. It’s always a stupid example form that was purposefully set up to be vulnerable to such injection attacks. I wish someone could show this working when someone uses proper input sanitization.
The longer I watched this the more upset I became at web development that 1. they're using direct string replace and 2. they didn't properly sanitize the input but then I became legitimately impressed with the use of the javascript uri the hex encoding, and the use of objects
Great video! Really well explained and easy to understand. Would like more in this series to just explain a short exploit in a way that anyone can understand.
Just make sure you're using built-in functions to filter user's input. In case of passing data to JS, it would be even better if you use JSON. For PHP it should look like this: x("a", ); Note the lack of double quotes in the second argument. That's because json_encode() wraps the value of $xss in quotes if it's a string.
This is a really cool format. Had this recommended, never seen your channel. Ngl I thought it was gonna be clickbaity and surface level, but this was great! I subbed
This mean TypeScript devs won't find this vuln, as they type the func to accept only N number of args, and TS will throw runtime error if they try to use N+K args, but in build time there code will create this vuln.
@@joechristo2 yeah but it can only type check intentionally authored code. TS will be no help at runtime against injected code, since that's all long after the type-checking time
As a Rust programmer, it blows my mind how messy Javascript has become. When a programming language gets obsessed with "convenience", it becomes impossible to keep track of changes. I think browsers should switch to simply running a WebAssembly runtime directly instead of Javascript.
Whatever technical things he say ( which is almost 95%) I don't understand a thing. Could someone help me to learn which tools, languages, etc to understand whatever he says ( at least like all those technical terms).
Why cyber security is hard to learn, when learning web development you ask a question and you get the answer, in cyber security you have no one to ask and you don't get the actually answer..
5:57 the screebshot at this timestamp may potentially help me with an eacape in a challenge I've left sitting. I can't seem to find any writeups past step 1 (clue 1) of the writeup. It's been a bitch.
Hi I'm a noob here. I think this is interesting but I don't see how this can be a vulnerability since it can only trigger on a client that you obviously have already access to...
Great video and explanation, professional, and gets to the point. I think one main takeaway one can get, that would especially help guys who may feel overwhelmed by these injections, is that the core problem here to be spotted while you are testing is the lack of the encoding / filtering of the double quotes, which allows you to escape the context of the string where the contents of the parameter is being injected. After that is just a matter of playing around to see what you are allowed to inject and find a way to run code, which is what these injections are all about.
Actually this is PHP problem, not JS. First of all you must escape correctly when transferring PHP variable to inline JS script. Using handmade regex is error-prone. Instead you can use json_encode() in PHP for that scenario. Here is the example: const foo = ; But still this is not totally safe, because it doesn’t escape , you can use additional flags for that. const foo = ; Anyway the XSS talked in this video is caused by misusing PHP and is not related to JS. It should be better to explain how to solve this in PHP instead of talking about JavaScript. Also some other programming languages for example Golang (.gohtml) implicitly json encode to safe string before printing your variable to script tag.
Bare json_encode would be enough. While it doesn't escape , it'll still escape slash. So becomes "", which doesn't close the script tag and stays a part of the string.
Why would it get automatically escaped by the input form. Or the correct question would be, why would it not get automatically escapes by PHP? Well. Because PHP doesn’t do that automatically. If you want that you need to program that
A couple of questions: When does the evaluation of the parameter takes place? Right after the function call and before any part of the function takes place? Are there any possible mitigations for this kind of exploit? I mean if this code runs before anything else I don’t see any possibility of mitigations which is wild, but I might be missing something
i have no idea what i’m talking about (as in the context of the video cuz i haven’t watched it) but JS might use C calling conventions in some cases i think (?) and with those, usually the parameters are passed to the function BEFORE the function gets “called” (as in the CALL assembly instruction) but it really doesn’t matter what the function “is” because it can be overrided to not even use the parameters in the first place but get called by the same name, which might be a security risk if some people don’t know what they’re doing
@@joechristo2 well in the video it’s shown that parameters are evaluated pre call to the function which causes a security risk at a fundamental level since the parameter inserted may contain js code that will run before the call of the function Maybe having input checks before each function calll can be a solution but still it seems clunky and weird
The assignment is evaluated before the function call. It has to because otherwise you couldn't use the return value of assignments in functions. The mitigation for this is to not have it in the first place e.g. sanitizing the userinput before placing it in the dom
For the first solution, what about using square brackets to define an array instead of an object? For the second solution, I believe the "new class b" part can be deleted if you replace the equals after toString with a colon. Great video!
Agreed that the toString in object literal should work too.... maybe they're trying to be general as far as including the case that different characters are prohibited (for example the colon). I think your suggestion with the array gives a nice way of solving it if curly braces are prohibited too.
@@KirkWaiblinger this! if colon is available, might as well use the first example. If it isnt, but one of many whitespace/line terminator/multiline comment characters are, we can use the second example. [location=name] is a good point!
but in lua members of objects are referred to by square brackets as WELL as members of arrays because every variable is an object in lua and every variable is an object in JS
the question is how you will control the window.open() ? probably it is gonna be hardcoded values. please someone explain, i couldn't understand that!!!
@@LiveOverflow I guess nothing gets "executed" because of the syntax error, but JavaScript does know in what order to execute this: first the concatenation, then the assignment. It just so happens that the expression makes no sense using that order
@@LiveOverflow My bad, I meant parsed, not executed. What I was trying to say is that the reason the expression in the video results in a syntax error is that the addition is treated as the left side of the assignment and is not assignable, and that it is similar to the 1 = 2 case in that regard. I looked it up in the ECMAScript documentation to try to be more precise this time and it seems that the reason it results in a syntax error is that the left side of the assignment is not a valid LeftHandSideExpression (13.3) or because of the second bullet in (13.15.1). The fun thing is that I actually tested that with " true ? 0 : (1 = 2) " before writing the comment and it did fail with a syntax error instead of executing.
This episode could have been 13m37s in length, surely...!
oooof.... missed opportunity
@@LiveOverfloweeh leet, leat, same thing
It must be an AI.
There is no way the Real liveoverflow would have ever let this slip,
He cut it, he render it, he watch it
He uploads it.
Multiple occasions where an Actual human would have seen the magical number but not an AI..
For an AI it's just a number.
Therefore Liveroverflow has replaced himself with an AI
could, but wans't
@@lukasjetu9776 I think Leet + 9 seconds bonus is also cool. Nice video, now I'm hungry for more XSS.
Most valuable piece of information I saw today
It feels like it's a special case of DOM Clobbering, right? We are overwriting the names/definitions of defined variables/functions with our payloads so that they get executed when the page's code calls the overwritten function without knowing it.
Nice video explaining the issue. One thing that I think is good to mention is what is the underlying mistake. This makes it a better resource for devs and also for researchers. In my humble opinion this is due to the fact that the person implementing this tried to it's own filtering instead of using the native available functionality and/or standard package. The red flag beeing the specific list of characters used for filtering
I'm really into all kinds of quirks of js and I can't believe that knowledge finally paid off and I was able to fully follow a liveoverflow video 🎉
Yea its one of the more easy to follow videos for web soydevs like us :D
It's such a weird filtering when you disallow ( ' and ` but allow " < and >
would also work in this example
I like this as a reoccurring video. It is nice to be able to decipher what someone was referring to. Given everyone has different levels of knowledge, I would give it a 2 thumbs up. Keep ‘em coming!
This is not really JS problems as some people seems to think. Carelessly treating user's input would always lead to big problems. In general when developing FE applications we rarely set any user provided values in any context that could be evaluated like this.
Concatenating user's input with code is just bad practice and big no-no.
In general, interesting information, but highly theoretical: so many characters are disallowed while double quote still being allowed. I feel IRL, if such case would be allowed, would be either no input cleaning or stricter rules.
Sadly most websites stubbornly develop their own ways of providing rich text display methods instead of using standards, which generally just tends to expose users to exploits... I know that all too well. Been working on the frontend for a while (please kill me)
I have seen a lot of old codebase concatenating user's input with code, it really isn't that bad as long as you know what you are doing. Also in those applications you just can't rewrite the majority of the codebase just to fix a newly discovered XSS.
Sorry I lied it was so damn bad that it has become a joke where the filter list just increases day by day. We slapped on a 5000$ IDS and IPS service and everyone pretends like everything is in control but deep inside we all know that the codebase is on fire. I know Robert had told me for a thousand time that concatenating user input with code is bad, but when deadline is chasing off my a** I just can't help but pray and do it anyway, I just want to go home.
Sorry Robert, I swear it will be the last time I do it.
Amen.
you are absolutely right. thats also almost always my first thought. but i have to throw that thought away for a moment because it gets more interessting if you think about all the existing websites who still could have flaws like this. and its also interesting just to see again how sh*tty and dirty compilcated and entangled javascript can be as a scripting language :D
it kind of is. javascript is dogshit and was made to do simple things when it was created but some clowns said "hold my beer" and other clowns took it seriously, then nodejs happened and embedded webshit posing as fully functional desktop applications known as electron came to be and it's at its worse. Thank God I don't ever was forced to dabble in this cesspool profesionally
as always Xcelent Xplanation....
PLEASE do more vids like these! I love the way you explained every bit.
This was super interesting and fun to learn about. Great lesson! Hope to see more of your content, keep up the great work
real hackers don't use Twitter/X anymore.. But Mastodon.
Cool, but not one programmer who respects himself will not write such a shit code.
I will say more, in order to allow such a vulnerability, you need to try hard
great video. learned a lot. would love to see more like it 👍
This video should have been "The Secret Step-by-step Guide to hacking: Deep Dive" 😂
Great video tho.
i refuse to create a twitter account, and twitter doesn't allow viewing without a account so. i can't look at the links you posted. at least Tiktok allows you to view stuff without requiring a account. but i hate tiktok
wow it's an awesome idea, I always took ton of researches to understand.
About using the name variable, wouldn't that only work on your window? I can't see how the xss would do something nefarious on a targets browser.
You link them to your website, that redirects with the name "parameter"?
@@schwingedeshaehers thanks i was confused
I’ve never seen an actual real world example of a successful XSS or SQL injection attack. It’s always a stupid example form that was purposefully set up to be vulnerable to such injection attacks. I wish someone could show this working when someone uses proper input sanitization.
Super interesting video, liked this very much!
In 2023, the only safe way to accept user input is via post letters
If I could I would subscribe again. :D
Love this explanation. Would use this as a quick explanation for javascript injection methods in general
The longer I watched this the more upset I became at web development that 1. they're using direct string replace and 2. they didn't properly sanitize the input
but then I became legitimately impressed with the use of the javascript uri the hex encoding, and the use of objects
Aren't there many other ways too? Like...
"[location=name],"
".a=location=name,"
A"?location=name:0,"
clever approach
neat! these tricks go straight into my notes ! Nice video format too. I'd like to watch more of this kind
Is this some sort of haXplaining ?
well that was useful who doesnt get anything
This would've been your chance to call it haXplained or heXplained.
Great video! Really well explained and easy to understand. Would like more in this series to just explain a short exploit in a way that anyone can understand.
Cool format, please more of this :)
Now if I make a website, how can I avoid exploits like this?
Just make sure you're using built-in functions to filter user's input. In case of passing data to JS, it would be even better if you use JSON. For PHP it should look like this:
x("a", );
Note the lack of double quotes in the second argument. That's because json_encode() wraps the value of $xss in quotes if it's a string.
This is a really cool format. Had this recommended, never seen your channel. Ngl I thought it was gonna be clickbaity and surface level, but this was great! I subbed
This mean TypeScript devs won't find this vuln, as they type the func to accept only N number of args, and TS will throw runtime error if they try to use N+K args, but in build time there code will create this vuln.
TS will not throw a runtime error if a function is called with extra arguments. At runtime it's just raw JS and anything goes.
@@KirkWaiblingertypescript is meant to PREVENT runtime errors from even happening
@@joechristo2 yeah but it can only type check intentionally authored code. TS will be no help at runtime against injected code, since that's all long after the type-checking time
super cool bug, and great explanation!
Yes, this video was funny, it was useful, and now I find javascript even much more strange than it already was.
Very insight and presented in a way you can understand. I had no idea about XSS or an and now I do.
same
Did I only understand about 20% of this? Yes.
Did I watch it all and want more anyway? Also yes.
That's crazy creative. I'd be interested in learning how this could be mitigated. Better input sanitation?
The conclusion is simple: Javascript is full of black magic!
If this amuses you, you have a lot to learn! And that's exciting
This was utterly amazing
What will be the use case and what it is use for.
Sorry just want to know/learn more, for me it looks useless to set an alert for myself
You can set any javascript instead of alert, so you can do anything at the server.
@@jaideepshekhar4621 so If someone else accesses the same page he will get the same script which I injected
As a Rust programmer, it blows my mind how messy Javascript has become. When a programming language gets obsessed with "convenience", it becomes impossible to keep track of changes. I think browsers should switch to simply running a WebAssembly runtime directly instead of Javascript.
people are gonna lose track of the difference between asmjs and wasm, thinking they are the same thing thus doing damage to the web as a whole
Loved it. Please continue.
thank you reminding me:
do. not. touch. javascript. ever. never. ever.
Whatever technical things he say ( which is almost 95%) I don't understand a thing. Could someone help me to learn which tools, languages, etc to understand whatever he says ( at least like all those technical terms).
learned more about java script in this video than i learned in year of college doing some shitty copypaste code :) ngl keep em coming
Why cyber security is hard to learn, when learning web development you ask a question and you get the answer, in cyber security you have no one to ask and you don't get the actually answer..
5:57 the screebshot at this timestamp may potentially help me with an eacape in a challenge I've left sitting. I can't seem to find any writeups past step 1 (clue 1) of the writeup.
It's been a bitch.
Wouldn't it be a little cleaner to just put the payload in an array like this: x(""+[location=name]) ?
This is great, Insiteful as always @LiveOverflow, can this type of xss vulnerabilities be found in react applications as well ?
Yes
if it runs javascript, it runs
Weak typing and its consequences have been a disaster for the human race.
Super interesting. Thanks for the explanation.
Super useful and interesting format. Thanks for sharing
Hi I'm a noob here. I think this is interesting but I don't see how this can be a vulnerability since it can only trigger on a client that you obviously have already access to...
I did my first JavaScript injection on a local realtor website when I was 10 ooops
This video started my web hacking journey, Thank you!
looking at the thumbnail i was like "he looks german" and well he got an german accent. Hallo fellow Deutscher
What are they really looking for in cyber security role? are the courses that we see online really enough? probably not even close, right?
Not even a minute of reproduction and I can say "I love this series"
What is a day life in a cyber security job? can you show a real examples of tasks and jobs?
Just build web applications in Rust/WASM
that’s FRONTEND (at least WASM)
Great video and explanation, professional, and gets to the point. I think one main takeaway one can get, that would especially help guys who may feel overwhelmed by these injections, is that the core problem here to be spotted while you are testing is the lack of the encoding / filtering of the double quotes, which allows you to escape the context of the string where the contents of the parameter is being injected. After that is just a matter of playing around to see what you are allowed to inject and find a way to run code, which is what these injections are all about.
Reminds me of SQL injecting and little Bobby Tables
you don't need to write , those tags are all optional and are inserted automatically
what is more annoying than character filtering? dompurify
If you tweet such a statement, you are assuming the target knows what you are trying to show.
But, is this like, preventable with input validation?
Wow thanks! It's so important for people to have a handle on this sort of thing so we can be aware of what we need to look out for when writing code.
You'd be a lot cooler if you didn't put your pronouns in your bio, he/him!
@.@ That name thing seems super exploitable
Actually this is PHP problem, not JS. First of all you must escape correctly when transferring PHP variable to inline JS script. Using handmade regex is error-prone. Instead you can use json_encode() in PHP for that scenario.
Here is the example:
const foo = ;
But still this is not totally safe, because it doesn’t escape , you can use additional flags for that.
const foo = ;
Anyway the XSS talked in this video is caused by misusing PHP and is not related to JS. It should be better to explain how to solve this in PHP instead of talking about JavaScript. Also some other programming languages for example Golang (.gohtml) implicitly json encode to safe string before printing your variable to script tag.
Bare json_encode would be enough. While it doesn't escape , it'll still escape slash. So becomes "", which doesn't close the script tag and stays a part of the string.
How can I land on the first cyber security job?
this was an open tab for so long. greatly explained !!
Hm does it make sense to cancel out name on top of each page (or can it CSPed?)
What if they use "htmlspecialchars" php function?
could you upload a video about how to learn effektively?
the hex encoding trick is impressive too.
This format is fun and useful, please do it again!
Would you be able to create an array, instead of an object?
very fun format! :) learnt a few tricks
Why would the input end up as ""..."" instead of "\"...\""? Why would the quotes not get automatically escaped by the input form?
Why would it get automatically escaped by the input form. Or the correct question would be, why would it not get automatically escapes by PHP?
Well. Because PHP doesn’t do that automatically. If you want that you need to program that
+{toString:e=>location=name}
-{toString:e=>location=name}
0>{toString:e=>location=name}
...etc
replace toString with valueOf or [Symbol.toPrimitive]
[...{[Symbol.iterator]:e=>location=name}]
1 instanceof {[Symbol.hasInstance]:e=>location=name}
Good usage for the new Twitter logo 👏👏
A couple of questions:
When does the evaluation of the parameter takes place? Right after the function call and before any part of the function takes place?
Are there any possible mitigations for this kind of exploit? I mean if this code runs before anything else I don’t see any possibility of mitigations which is wild, but I might be missing something
i have no idea what i’m talking about (as in the context of the video cuz i haven’t watched it) but JS might use C calling conventions in some cases i think (?) and with those, usually the parameters are passed to the function BEFORE the function gets “called” (as in the CALL assembly instruction) but it really doesn’t matter what the function “is” because it can be overrided to not even use the parameters in the first place but get called by the same name, which might be a security risk if some people don’t know what they’re doing
@@joechristo2 well in the video it’s shown that parameters are evaluated pre call to the function which causes a security risk at a fundamental level since the parameter inserted may contain js code that will run before the call of the function
Maybe having input checks before each function calll can be a solution but still it seems clunky and weird
The assignment is evaluated before the function call. It has to because otherwise you couldn't use the return value of assignments in functions.
The mitigation for this is to not have it in the first place e.g. sanitizing the userinput before placing it in the dom
Can I bypass router login page
For the first solution, what about using square brackets to define an array instead of an object?
For the second solution, I believe the "new class b" part can be deleted if you replace the equals after toString with a colon.
Great video!
Agreed that the toString in object literal should work too.... maybe they're trying to be general as far as including the case that different characters are prohibited (for example the colon). I think your suggestion with the array gives a nice way of solving it if curly braces are prohibited too.
@@KirkWaiblinger this! if colon is available, might as well use the first example. If it isnt, but one of many whitespace/line terminator/multiline comment characters are, we can use the second example. [location=name] is a good point!
but in lua members of objects are referred to by square brackets as WELL as members of arrays because every variable is an object in lua and every variable is an object in JS
the question is how you will control the window.open() ? probably it is gonna be hardcoded values. please someone explain, i couldn't understand that!!!
You execute this from your own domain. So the victim visits your site and you trigger that
typical javascript error oh no
Great video, thanks!!
great video, thank you
9:00 Concatenation is executed first and the result is a string, which cannot be assigned to. It's essentially equivalent to writing 1 = 2
No, because you get a syntax error ;)
@@LiveOverflow I guess nothing gets "executed" because of the syntax error, but JavaScript does know in what order to execute this: first the concatenation, then the assignment. It just so happens that the expression makes no sense using that order
@@LiveOverflow My bad, I meant parsed, not executed.
What I was trying to say is that the reason the expression in the video results in a syntax error is that the addition is treated as the left side of the assignment and is not assignable, and that it is similar to the 1 = 2 case in that regard.
I looked it up in the ECMAScript documentation to try to be more precise this time and it seems that the reason it results in a syntax error is that the left side of the assignment is not a valid LeftHandSideExpression (13.3) or because of the second bullet in (13.15.1).
The fun thing is that I actually tested that with " true ? 0 : (1 = 2) " before writing the comment and it did fail with a syntax error instead of executing.
just ask chatgpt to explain it
I'm still waiting for it to run on twitter
Man, I almost never do websec, so this was fascinating. I learned a ton, your content is always top notch! Thanks for this ❤
Thank you for the information
Please make more vids like this!
You are genius thats all i have to say