Twitter XSS Vulnerability Still Wide Open, Developer Says

A software developer is claiming Twitter's fix for a critical cross-site scripting bug is no good, meaning users are still vulnerable to an attack that could allow an attacker to take over their accounts.

The bug was first reported by techie James Slater. According to Slater, the vulnerability allows malicious JavaScript to be inserted into tweets by adding the code to a field of the API used by Twitter developers. By embedding links in tweets, developers can direct Twitter users to their Websites.

More information on the Twitter vulnerability can be found here. At the heart of the issue seems to be that Twitter's API does not filter malicious URLs.

"Twitter made one of the most basic mistakes in developing Web applications—never blindly trust data that is provided from the outside world! Their form did no—or some very, very basic—checking on what you enter in the box," Slater wrote.

He said although Twitter claimed to have fixed the problem after he pointed it in a blog post Aug. 25, the fix did not address the issue.

"With a few minutes' work, someone with a bit of technical expertise could make a Twitter 'application' and start sending tweets with it … it can be arranged so that if another Twitter user so much as sees one of these tweets—and they are logged in to Twitter—their account could be taken over," Slater wrote.

A Twitter spokesperson did not respond to a request for comment. Slater advised Twitter users to "unfollow" anyone they don't know or trust.