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Cross-Site Scripting Hits Major Sites
An anonymous reader writes "Dark Reading and SC Magazine covered a story about hackers posting cross-site scripting (XSS) vulnerabilies en mass on dozens of high profile websites including Dell, MSN, HP, Apple, Myspace, YouTube, MSN, Cingular, etc. The media coverage drew the hacker's attention to the publication's websites where they got a taste first-hand. On message board wall-of-shame is PC World, MacWorld, Fox News, the Independent, and ZDNet UK. "...not only did we get the "scoop" on the XSS site problems, but we also got the message loud and clear: Don't assume you're immune to XSS vulnerabilities. They're everywhere." The news comes shortly after Mitre (CVE) released statistics showing XSS has become the most popular exploit. Unfortunately new XSS attacks are growing increasingly severe and scanners are unable to find many of the issues on modern websites."
The Cross Site Scripting FAQ
Believe me, if I started murdering people, there would be none of you left.
document.write("It's very hard to check for XSS. I can understand why most people don't bother.")
The reason most vuln scanners can't find XSS vulns on modern sites is because of the increased amount of JavaScript and Flash (with ActionScript) that's in use. But some scanners can grok this stuff to varying degrees of completeness.
Have you ever read poorly-written, newbish code?
For anything non-trivial, it would probably be quicker and cheaper to have the "pro" write the code in the first place than to pay him for his time to read, understand, and correct a steaming pile of turd spaghetti.
.. XSS links YouTube
my capcha was condom
Actually, CS 101 is data types and algorithms. Earning my CS degree taught me little of input validation. Most programmers learn security in one of two ways: proactively reading up on it or having one of their applications hacked. Unfortunately I think many average programmers don't consider input validation as much of a priority until after a hole they provided is exploited. When I ask many web developers what they do to prevent SQL injection attacks, for example, only about half have even considered it. Scary.
Developers: We can use your help.
Draw you own conclusions from there...
...quicker, easier, more seductive the darkside is...but more powerful, it is not.
...remains unaffec... FOJSF{09fiE*EU90av['vlwIOA934MAwadpskf[aepfkfa[-09 u9a
GetOuttaMySpace - The Anti-Social Network
Web 1.0: Simple fishing scam
Web 2.0: Cross-Site Scripting
That's it. They allow users in forum to post links, and URL. URL can have a lot of strange characters in it, & ? ! # etc... Apparently, the basis of XSS is to make a link that appears like a valid URL but that will, in some clients, execute as a javascript code, usually in order to steal cookies (therefore, an opened session) of the user watching the post. There seems to be a shield vs sword thing growing between attackers and web developers. You have numerous ways of "hiding" a code in an URL, hexadecimal notation, strange utf-8 characters and so on. Here again, an incomplete implementation of a standard is the cause of major headaches.
The Wise adapts himself to the world. The Fool adapts the world to himself. Therefore, all progress depends on the Fool.
Before web designers blame themselves for this, the existence of XSS is really a fundamental design flaw in the way JavaScript and browsers work. It should have been obvious as soon as JavaScript came out that these kinds of attacks would become a major issue over time, but the "ooh shiny" attitude of the computer industry meant that people adopted JavaScript without knowing what the implications were. In fact, the other big security hole and productivity drain of the industry, C/C++, got adopted in a similar way.
Writing any substantial piece of software in C, C++, or JavaScript without creating safety or security issues is extremely expensive and beyond the ability or resources of most developers. For C and C++, there are alternatives you can choose today. For JavaScript, you just have to minimize its use or simply not worry about it and let the client fix it with tools like NoScript.
"Web design" is for aesthetics and graphics people, like "interior design". Of course you run into problems when you have a web designer doing development work!
As for "No web developer has written XSS vulnerable code since 2002", I refer you to The Daily WTF.
http://outcampaign.org/
but it's probably pointless. Not enough developers care about their craft.
There's a prominent "popular science" website out there (no, it's not this one that I'm thinking of) that has ENORMOUS XSS vulnerabilities in its image gallery. They pass captions and img src in URL encoded query string parameters. Yuck.
I noticed this about a year ago and reported it to the development team, with a demonstration link that put in a (sorta not nice) image and caption. No response, and when I checked six months ago the vulnerability was still there. So much for being a nice guy.
Maybe I lucked out with a particularly cluefull teacher, but input validation was beaten into me learning Basic on an Apple II(e?) in high school: everyone fails the first round of the Craps game assignment when the teacher asks "what happens when I bet a negative amount?".
It looks like the attacks can be prevented by simple user input validation. Are the above mentioned high profile website developers/architects being too lazy or nobody knew about this type of vulnerability until recently ? I cant see how Joe Average will know about this exploit because he will not bother to read the query string(or even understand what it does) if it points to major website.
I've seen the interesting effects of this first hand with a customers server, which I was tasked to unhack. Took a while to spot the reason the server was hacked because stupidly I didn't think of XSS when I considered the range of hacks that had occurred. When I did finally start grepping the access_logs and saw the rather odd things being passed through an enquiry form script things started to piece together. I've filched a copy of the script passed and its quite impressive, though its probably reasonble to stake a claim on the hacker not being the script writer given the sheer wealth of comments and how to customize tips present. n00bishly (but then I'm not employed to harden boxes, nor am I a website programmer) I didn't expect a site to be quite so vulnerable to such a range of exploitation through XSS. The script I have includes stuff to exploit unpatched mysql to create new users, passes a load of hex strings I won't even hazard a guess at their purpose etc. etc. :)
As a geek I appreciate it the technical qualities, as the guy who had to unhack an exploited server however..
You could probably take a random blob of ones and zeros, run multiple instances of it as an executable image while randomly tweaking bits until you evolved a real executable, far faster than you could analyze some of the code I've had to replace over the years.
- Always use parameterized queries and never construct your own queries by concatenating strings. This will not only speed up the application, it will make sql injection attacks a non-issue
- Always verity the users input. You never know what the user is going to try to do with bad input.
- When programming in languages like C, always check to ensure that the user can't perform a buffer overflow attack.
I'm sure there's a lot of other things that people could add to this list. There's a lot of mistakes that happen over and over again. And I don't think that it's because people don't care, or aren't smart enough, but simply because they don't know the problem exists.Anthropic principle: We see the universe the way it is because if it were different we would not be here to see it.
The problem from what I have seen is in the attitude of the people running the websites. Their attitude tends to be that cross-site scripting doesn't directly impact their servers but only impacts the systems viewing the website. Since this doesn't have a direct impact on their server's it's not a high visibility threat to them. Their attitude towards their visitors is "We are secure but it sucks to be you."
"Anything tastes good if you deep fry it."
The biggest problem is farming everything in the world out to $8/hr guys in some foreign country. If you pay $8/hr, you're going to get an $8/hr guy. Keep in mind that Wal-Mart starts at $9/hr. Given these two statements, I fail to see why it's surprising that such simply fixed vulnerabilities continue to plague software.
2 cents,
QueenB
HDGary secures my bank
A) It's just as simple to prevent an SQL injection attack. Failing to clean your input is just a stupid mistake, regardless of the input method. Mistakes happen, but let's not pretend that input validation is complicated.
B) The reason people like to build web interfaces is that the client, server, and transfer mechanism already exist. Writing a new one for each project is much, much more work.
I say this because people need to be aware that links are not the only vector. My favorite one I've seen so far is <bgsound src='javascript:bad_code()'>. If you choose poorly and are trying to filter out bad tags (instead of what you should be doing, specifying only exactly what tags and attributes are allowed and forbidding anything else that looks like a tag), did you remember to block out the BGSOUND tag? If not, that auto-executes; it doesn't even need to be clicked. (IE may have closed that; I saw this in the IE 4 era.)
I'm a web developer and I've said this dozens of times.
VALIDATE ALL INPUT EVERYWHERE.
Validate on the client. (For bandwidth reduction)
Validate at the APP Tier (For security)
Validate at the Data Tier(For security and integrity)
If you accept input from a web page, scrub it, and that doesn't mean stripping brackets or quotes, it means putting in a list of valid characters and tossing or replacing absolutely everything else.
Yes, you might wind up validating something that doesn't need to be validated or scrubbing something that doesn't need to be, the performance hit is worth it.
Also, Stored Procedures are a great resource, if you design them properly you add an extra layer of security that can actually improve your application performance. (All my recent projects have Stored Procedure execute only rights.
If your db code has select * from table in it, you're doing it wrong.
Ok, enough ranting from me.
As a content manager for the U of Rochester when I was a student there, I witnessed thousands of attempts at XSS every month. All of this thanks to one idiot who decided he wanted to put a mambo website up on the student activities server, we had our main server breached and multiple websites defaced. once you're breached, everyone wants to try to hack you again. One interesting thing I noticed is that the majority of XSS attempts will try to call a script in a file with a .gif or .jpg name. This way, if a curious person sees the attempt and tries to visit the linked script, all they get is a broken image. However, the file_get_contents php function, or other such functions, will read those as PHP. I've seen these scripts uploaded to government websites, university servers and many other places. The one that was put on the U of Rochester server attempted to delete all of the files on the server and put in code for what looked like a perl proxy server (i dunno, it was kinda obfuscated, and I'm not too good at perl yet).
The XSS scripts are quite complex, too. Some of them create HTML/javascript console interfaces for people to interact with the server as if they had an SSH connection.
And they're all over the place. I've got a website that's had less than 1000 hits, and I've seen three separate attempts to use XSS on it.
How many "web" templating systems do you know that automatically escape HTML unless told otherwise? I know of one that can be made to do so: Mason. Even then, you have to enable it, as it's not turned on by default.
What about PHP, ASP, JSP and so on? Will they ever grow up and automatically escape HTML by default? I doubt it very much.
In the meantime, there's always mod_security if you're willing to invest the time configuring it. But it's no guarantee...
-Dom
The problem isn't that they didn't validate the user input, so much as that validating user input is really, really hard. RSS aggregators are discovering the problems with validating that HTML is safe. See http://www.feedparser.org/docs/html-sanitization.h tmlt yles-as-part-of-sanitation/
The trouble is that an approach like that limits what you can do too much: http://www.symphonious.net/2006/09/10/stripping-s
Any site that wants to support formatted comments, like Slashdot, has to deal with this. The plus side when it's just comments is that you can have very draconian limitations to what's accepted without it getting in the way (like Slashdot does).