In this specific case merely forging a POST request externally does nothing as the user has to be signed in for this to work. Thus, restricting actions such as voting to POST (and restricting to same-origin) does constitute adequate protection if there is no XSS vulnerability on the site.
But if the user IS signed in (and if someone arrives at your site from a link on Hacker News there's a very good chance they will be signed in) a POST forged from your site can affect their session. Read up on CSRF - it's a very different vulnerability from XSS (though having an XSS vulnerability will make any CSRF protection you have in place null and void).
So that anyone who has JavaScript disabled will be treated like an attacker? No thanks, HN is one of very few sites nowadays that work fine without JavaScript tricks, and I'd much rather PG kept it that way.
That's not a good enough solution - there are decent reasons that a referrer header might be missing (some PC antivirus software strips out referrer headers for example). The only safe way to handle this is with a POST request protected by a CSRF token tied to a cookie.
This doesn't really apply when you are trying to verify whether the client actually performed some action.
In a CSRF scenario, the client itself can presumably be "trusted" - A client behaving maliciously can only hurt itself, not any one else. The important thing is to not trust anything that may have been provided by a third party.
"It's all about the execution", "Usability counts", "Ideas are worthless", yadda yadda... Joking aside, congrats on finding the bug. I would send you the karma if I could!
EDIT: You are welcome. I am not sure this is comprehensive either, though. For one it will only include submissions with a space in the title, I think.
An interesting side effect may be to drive registrations, as it will appear to non logged-in users that they have to create an account before viewing the #1 item.
The easiest way to do it would be to pick an ID in the future (say 20 ahead of the latest one) then type the title and link out, then just keep refreshing the page for your selected ID minus one (for example, if your chosen ID is 3743040 refresh news.ycombinator.com/item?id=3743039) until you get a result then hit submit, if you're not too slow you'll get the ID 3743040.
When I saw the first one of these, I thought to myself that the front-page wouldn't be overwhelmed by these posts. The whole reason most of us are here is that it is a mature community. As the first post was enough to prove the point, why did OP post it again? (S)He apologize and give credit to "http://news.ycombinator.com/item?id=3742742 (GreekOphion) for finding the bug", but why make the post at all? What good does it do? "I would send you the karma if I could!" just seems disingenuous.
A slightly unrelated question: What's up with those non-votable non-commentable recruiting links that have been up on the front page recently? Was that another bug exploit?
I can't help but wonder if someone discovered this before, and realised they'd need to put some sort of throttling in place to keep it under the radar…
(Maybe _that_ explains why so many TechCrunch articles make the front page?)
You could send it to a link which is hooked to a script that swaps the links for one in ten views or what have you. The extra benefit of that approach is that you don't have to worry about getting the submission ID right when submitting. You can just edit it on your server retroactively.
Not that I'd ever be crazy enough try this for real of course.
EDIT: According to posts I've read the votes aren't valid if the referrer isn't Hacker News. So the only thing possible is what's on display.
You can see it in the url here because he wasn't trying to hide it. He could have linked to a blog post containing a hidden element that does the get (after checking if the referer is HN).
I'm curious as to whether this post will ever leave the front page. If it keeps getting points at an alarming rate, is there anything in the algorithm to eventually lower the ranking?
I think I remember seeing a post just like this a couple of years ago, after which the bug was fixed. I wonder if there was a regression or if this is somehow different.
I think you need to set "showdead" in your profile to see this. It got killed pretty quickly, but netted me ~150 karma which was amusingly nontrivial back then. And as a byproduct, I think I became the first "public member" to get a glimpse of Arc, which was closed-source at the time. I won't disclose how (since I haven't asked for permission to share the details) but it was pretty much one of the happiest days of my life, for some stupid reason. I was young and giddy and felt like I'd just won something special.
To give you an idea of how ancient this is, check out the id of the thread -- only #27,615. Man, time flies when you're watching a community grow, eh? It's like watching a child mature over years -- into an increasingly-annoying version of themselves while slowly getting fatter and fatter over the years, of course. (I kid, I kid.)
Bonus: I just now noticed that I'd gotten into a debate with Paul B in that thread. Hah. I was too cocky back then... I should have been listening and asking questions, not talking!
Man, I miss those days so much. I never knew how rare they were until they were gone. Like, my girlfriend (now wife) and I went on vacation, during which we prototyped and launched a whole webapp in Rails 1.0! Who does that? Not me, anymore -- At least, not until I lose my day job like a bad case of music. Makes me wonder if I still have my old "hey, I'm 18 and ignorant of my own flaws!" level of productivity...
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EDIT: Oh, look. I have the attention of the majority of HN. Allow me to now exploit you:
To whomever has read upto here: you hereby implicitly agree my EULA, in which you swear to enjoy each of your scientific pursuits with intensity and to your fullest degree; and sometimes even to a dangerous degree, if the mood carries you thus. Additionally, you agree to never allow an employer, family member, or any other authority to break your intrinsic spirit; for they have no means of dominating your spirit except that which you subconsciously allow them. You shall be true to yourself and to your own principles, regardless of society (though in privacy). You shall hereby refuse to believe any scientific statement as "true", however benign, except those in which you alone have proven to yourself to be true, by your own hand and evidence. (Though it doesn't hurt to check out what other people have to say on the subject, from time to time; in fact, it turns out to often be a more valuable course of action, for the careful analysis of a close friend can often reveal subtle flaws in your process and in your logic, while occasionally forcing you to re-evaluate your core reasoning for choosing that process in the first place, which always leads to the path of learning and thus improvement and satisfaction.) You agree to eventually die with no regrets. Let no one impose themselves upon your judgement without merit. You shall endeavor to enjoy life to the fullest extent of the law (where applicable), and to realize that money is merely a means, not an end unto itself. In your spare time, you shall research that which is impossible, but intriguing, in order to always have something to strive for, thereby improving your skill and your spirit. You shall follow your curiosity wherever it leads (but keep both eyes open for signs of danger).
Most importantly: thou shalt enjoy every week, else thou shalt fix your life's situation regardless of how immutable it may seem.
> Bonus: I just noticed I'd gotten into a debate with Paul B in that thread. Hah. I was too cocky back then... I should have been listening, not talking!
OT but funny story: back when I was first getting into programming heavily (I had dabbled for about 4 years, but wasn't particularly good), I started learning perl, and got into a flame war on freenode with some random guy I had never seen on before (in the three times I had visited). It was weird - everybody sided with him, so strongly that I was really confused. His username was strange, too - something about "toady".
Yup, I, a perl programmer of 2 weeks, got into a flame war with Larry Wall. Didn't realize it for years, until I saw his IRC nick mentioned somewhere else. Ouch.
