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Security researchers have revealed that the websites of no less than six anti-virus firms are vulnerable to cross-site scripting flaws, of a type that might lend themselves to phishing attacks.

Some of the firms involved have admitted problems, while others say the issues raised have either already been fixed or are erroneous.

Nemesis, a gang of programmers and security bods that work mostly in chat room software development, reckons the sites of Symantec, Kaspersky, Eset (Nod32), AVG, F-secure and Trend Micro are all vulnerable, one way or another. The group has posted screen shots to back up its claims in an advisory here.

El Reg contacted the six firms involved on Monday evening, some of who have already got back to us. We'll add statements from the others as and when they become available.

* Trend Micro said the flaw highlighted by Nemesis is on a part of its site which is outsourced. The firm added that the flaw was in the process of getting fixed.
* Eset said the site with the alleged flaw, eset.co.il, was run by its Israeli distributor. "The iFrame injection has been removed from eset.co.il and today (Tuesday) the site will be deeply scanned to fix all other possible vulnerabilities," it said in a statement.
* Symantec said the reported vulnerability on its site was discovered and fixed last month. "Symantec was notified of a reported security vulnerability on a webpage within Symantec's website back in April," a spokeswoman explained. "Upon notification of the potential vulnerability, Symantec immediately conducted comprehensive testing and fixed the vulnerability. Symantec takes the security of its website very seriously and can confirm that no company or customer information was exposed."
* AVG said there wasn't any problem with its site. “We’ve investigated the issue as raised by The Register, and we can report that there is no vulnerability on the AVG website. We’re always looking at potential security issues – and extra ways to keep our customers’ data secure. As an internet security company, we often find that we come under attack from the bad guys."

Broadly speaking the cross-site scripting flaws detailed by the Nemesis make it possible to present rogue iFrames from third-party servers as if they came from the sites of security vendors a surfer might be visiting. This type of vulnerability therefore lends itself to attacks that rely on impersonation, such as phishing. XSS flaws, more generally, also pose cookie stealing and other risks.

This class of vulnerability has popped up on the website of security firms over recent months. Most notable Romanian hacking group HackersBlog exposed XSS flaws on the websites of Kaspersky, BitDefender, F-Secure and Symantec in a two month campaign before the group got bored and disbanded in late March 2009.

Other incidents of similar problems on the websites of McAfee and Symantec have cropped up since to the point where its tempting to think that the problem has become endemic.

http://www.theregister.co.uk/2009/05/12/av_xss_six/