Sure, third-party services like the OP can provide bots that can scan. But if you create an ecosystem in which PRs can be submitted by threat actors, part of your commitment to the community should be to provide visibility into attacks that cannot be seen by the naked eye, and make that protection the norm rather than the exception.
[0] https://docs.github.com/en/get-started/learning-about-github...
It makes the product better
So I'd argue it's the responsibility of the developers, hired by GitHub, to create this feature because it makes the product better. Because that's the thing you've been hired for: to make the product better. Your concern isn't about the money, your concern is about the product. That's what you're hired for.
See commenter on their 2025 bounty for reporting it, won't-fix resolution: https://news.ycombinator.com/item?id=47393393
i see squares on a properly configured vim on xterm.
https://docs.github.com/en/authentication/managing-commit-si...
I first heard about the possibility of this kind of attack >10 years ago, and I'll sometimes do a xxd if i'm feeling a bit paranoid.
The mere fact that a software maintainer would merge code without knowing what it does says more about the terrible state of software.
I don't know if it is relevant in any specific case that is being discussed here, but if the exploit route is via gaining access to the accounts of previously trusted submitters (or otherwise being able to impersonate them) it could be a case of teams with a pile of PRs to review (many of which are the sloppy unverified LLM output that is causing a problem for some popular projects) lets through an update from a trusted source that has been compromised.
It could correctly be argued that this is a problem caused by laziness and corner cutting, but it is still understandable because projects that are essentially run by a volunteer workforce have limited time resources available.
Of course, it doesn't work though. I reported this to their bug bounty, they paid me a bounty, and told me "we won't be fixing it": https://joshua.hu/2025-bug-bounty-stories-fail#githubs-utf-f...
The exact quote is "Thanks for the submission! We have reviewed your report and validated your findings. After internally assessing your report based on factors including the complexity of successfully exploiting the vulnerability, the potential data and information exposure, as well as the systems and users that would be impacted, we have determined that they do not present a significant security risk to be eligible under our rewards structure." The funny thing is, they actually gave me $500 and a lifetime GitHub Pro for the submission.
The article is about in JavaScript, although it can apply to other programming languages as well. However, even in JavaScript, you can use \u escapes in place of the non-ASCII characters. (One of my ideas in a programming language design intended to be better instead of C, is that it forces visible ASCII (and a few control characters, with some restrictions on their use), unless you specify by a directive or switch that you want to allow non-ASCII bytes.)
Same. And I enforce it. I've got scripts and hooks that enforces source files to only ever be a subset of ASCII (not even all ASCII codes have their place in source code).
Unicode chars strings are perfectly fine in resource files. You can build perfectly i18n/l10n apps and webapps without ever using a single Unicode character in a source file. And if you really do need one, there's indeed ASCII escaping available in many languages.
Some shall complan that their name as "Author: ..." in comments cannot be written properly in ASCII. If I wanted to be facetious I'd say that soon we'll see:
# Author: Claude Opus 27.2
The biggest use of Unicode in source repos now might be LLM slop, so I certainly don't miss its absence at all.
The malicious code was introduced in this commit - https://github.com/pedronauck/reworm/commit/d50cd8c8966893c6...
It says coauthored by dependabot and refers to a PR opened in 2020 (https://github.com/pedronauck/reworm/pull/28).
That PR itself was merged in 2020 here - https://github.com/pedronauck/reworm/commit/df8c1803c519f599...
But the commit with the worm (d50cd8c), re-introduces the same change from df8c180 to the file `yarn.lock`.
And when you look at the history of yarn.lock inside of github, all references to the original version bump (df8c180) are gone...? In fact if you look at the overall commit history, the clean df8c180 commit does not exist.
I'm struggling to understand what kind of shenanigans happened here exactly.
Notice that the original commit is verified: https://github.com/pedronauck/reworm/commit/df8c1803c519f599...
While the malicious one is not: https://github.com/pedronauck/reworm/commit/d50cd8c8966893c6...
I still don't quite understand what GitHub is doing to allow someone to say that dependabot coauthored a spoofed commit. This isn't the commit message itself I'm talking about. It's the GitHub interface that officially recognizes this as a dependabot co authored commit. My hunch is that the malicious author squashed two commits, the original good commit to yarn.lock and a malicious change to package.json, and that somehow maintains the dependabot authorship instead of reassigning it fully to the squash-er.
Innocuous PR (but do note the line about "pedronauck pushed a commit that referenced this pull request last week"): https://github.com/pedronauck/reworm/pull/28
Original commit: https://github.com/pedronauck/reworm/commit/df8c18
Amended commit: https://github.com/pedronauck/reworm/commit/d50cd8
Either way, pretty clear sign that the owner's creds (and possibly an entire machine) are compromised.
But really, it still has to be injected after the fact. Even the most superficial code review should catch it.
Like the following example (you can paste it into node to verify), could be spread out over multiple source files to make it even harder to follow:
// prelude 1, obfuscate the constructor property name to avoid raising simple analyser alarms
const prefix = "construction".substring(0,7);
const suffix = "tractor".substring(3);
const obfuscatedConstructorName = prefix + suffix; // innocent looking, but we have the indexing name.
// prelude 2, get the Function class by indexing a function object with our constructor property name (that does not show up in source-code)
const existingFunction = ()=>"nothing here";
const InnocentLookingClass = existingFunction[obfuscatedConstructorName];
// payload decoding elsewhere (this is where we decode our nasty source)
const nastyPayloadDisguisedAsData = "console.log('sourced string that could be malicious')";
// Unrelated location where payload gets executed
const hardToMissFun = new InnocentLookingClass(nastyPayloadDisguisedAsData);
hardToMissFun(); // when this function is run somewhere.. the nasty things happen.
Yes, it's a red flag. Yes, there's legitimate uses. Yes, you should always interrogate evals more closely. All these are true
Sure the payload is invisible (although tbh im surprised it is. PUA characters usually show up as boxes with hexcodes for me), but the part where you put an "empty" string through eval isn't.
If you are not reviewing your code enough to notice something as non sensical as eval() an empty string, would you really notice the non obfuscated payload either?
It sounds like Python only allows approved Unicode characters to start a variable name but if it allowed any you could do something like `nonprintable = lambda x: insert exploit code here`. If that was hidden in what looked like a blank line between other additions would you catch it?
I'm sure there's some other language out there that has similar syntax and lax Unicode rules this could be used in.
The solution is that this and many other Unicode formatting characters should be ignored and converted to a visible indicator in all code views when you expect plain text.
This isn't about formating characters, this is about private use characters.
For data or code hiding the Acme::Bleach Perl module is an old example though by no means the oldest example of such. This is largely irrelevant given how relevant not learning from history is for most.
Invisible characters may also cause hard to debug issues, such as lpr(1) not working for a user, who turned out to have a control character hiding in their .cshrc. Such things as hex viewers and OCD levels of attention to detail are suggested.
Then, any appearance of unprintable characters should also be flagged. There are rather few legitimate uses of some zero-width characters, like ZWJ in emoji composition. Ideally all such characters should be inserted as \xNNNN escape sequences, and not literal characters.
Simple lint rules would suffice for that, with zero AI involvement.
Emojis are another abomination that should be removed from Unicode. If you want pictures, use a gif.
I have considered allowing a short list that does not include emojis, joining characters, and so on - basically just currency symbols, accent marks, and everything else you'd find in CP-1521 but never got around to it.
Lint zero-width chars, sure. But if the actual sink is runtime string injection, banning eval is only half a fix because Function and friends still get you to the same bad place while the linter congratulates itself.
grep -P '[\x{200B}\x{200C}\x{200D}\x{FEFF}]' code.ts
And please, everyone arguing the code snippet should never have passed review - do you honestly believe this is the only kind of attack that can exploit invisible characters?
Is there ever a circumstance where the invisible characters are both legitimate and you as a software developer wouldn't want to see them in the source code?
And, yes, there is a circumstance if you want to include Arabic or Hebrew in comments or strings. You need the zero width left-right markers to make that work.
Looks like it's pilfering Solana wallets that don't belong to Russians.
Claude’s analysis seems solid here based on reading the snippets it tested.
A purpose-built linter could be cross-language, it’s pretty reasonable to blanket ban these characters entirely, or at least allowlist them.
Things that vanish on a printout should not be in Unicode.
Remove them from Unicode.
Unicode needs tab, space, form feed, and carriage return.
Unicode needs U+200E LEFT-TO-RIGHT MARK and U+200F RIGHT-TO-LEFT MARK to switch between left-to-right and right-to-left languages.
Unicode needs U+115F HANGUL CHOSEONG FILLER and U+1160 HANGUL JUNGSEONG FILLER to typeset Korean.
Unicode needs U+200C ZERO WIDTH NON-JOINER to encode that two characters should not be connected by a ligature.
Unicode needs U+200B ZERO WIDTH SPACE to indicate a word break opportunity without actually inserting a visible space.
Unicode needs MONGOLIAN FREE VARIATION SELECTORs to encode the traditional Mongolian alphabet.
I should be able to use Ü as a cursed smiley in text, and many more writing systems supported by Unicode support even more funny things. That's a good thing.
On the other hand, if technical and display file names (to GUI users) were separate, my need for crazy characters in file names, code bases and such are very limited. Lower ASCII for actual file names consumed by technical people is sufficient to me.
Sure, but more crazy stuff gets added all the time.
Rule of thumb: two Unicode sequences that look identical when printed should consist of the same code points.
And, for example, Greek words containing this letter should be encoded with a mix of Latin and Greek characters?
Some middle ground so that you can use greek letters in Julia might be nice as well.
But I don't see any purpose in using the Personal Use Areas (PUA) in programming.
Do you honestly think this is a workable solution?
Also this attack doesnt seem to use invisible characters just characters that dont have an assigned meaning.
I am wondering how that they've LLM, are people using them for making new kind of malicious codes more sophisticated than before?
Besides, that's why the ban only extends to syntax and string literals (use escapes instead), and not comments.
From my experience, the only two nationalities that insist on mixing their native languages with the mostly English syntax of programming languages are the French and the Japanese. And they can just suck it up for the other 8 billion of us.
Are people using eval() in production code?
My clawbot & other AI agents already have this figured out.
/s