Researchers Find Critical XSS Vulnerability in Tumblr

The flaw could be leveraged to steal user cookies and more

By Eduard Kovacs on June 11th, 2012 07:28 GMT

Independent Indian security researchers Aditya Gupta and Subho Halder have identified a dangerous cross-site scripting (XSS) vulnerability in the popular blog hosting platform Tumblr.

According to the experts, the security hole is not something that should be left unaddressed since it poses a lot of risks for the site’s customers. The screenshot provided by the researchers shows how the vulnerability could be leveraged.

“As you can see, I could get the cookies of any user who visits my profile page. They are the actual Tumblr authentication cookies, which means I could use the cookies to login to the respective user accounts,” Gupta explained.

And apparently stealing user sessions is not the only thing that could be achieved by using this weakness. An attacker could leverage this flaw to cause even more serious damage.

“Also, I could make a complete worm out of it, so when one person views my profile, he would repost my post and everyone in his list who would see it would then be doing the same. All automatically and without the user’s knowledge,” he told us.

While the vulnerability seems highly dangerous, the researchers claim that so far Tumblr has ignored their findings.

“I have tried to contact them via Twitter and mail earlier, but no response from their side. So we have decided to release it. Well, not exactly where the vulnerability is, but just to let them know that it is vulnerable,” Gupta said.

Hopefully Tumblr will act on addressing the issue before a cybercriminal mastermind sees a “business opportunity” in it.

The experts have provided a working proof-of-concept, which of course we will not make public, at least not until the bug is fixed.
Proof of vulnerability in Tumblr
   Proof of vulnerability in Tumblr
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