Twitter explains “onMouseOver” security flaw



Yesterday, thousands of Twitter users found themselves redirected to other websites, and that they were automatically sending tweets to  to others due to  a security hole on Twitter’s website.

The attack was caused by malicious users using cross-site scripting (XSS) and it was particularly worrying because it could be exploited simply by hovering over a link on a page. In some cases, merely visiting the Twitter user homepage was enough to set off a pattern of auto tweets.

Twitter security team member Bob Lord had explained about the breach on Twitter’s official blog. “The security exploit that caused problems this morning Pacific time was caused by cross-site scripting (XSS). Cross-site scripting is the practice of placing code from an untrusted website into another one. In this case, users submitted javascript code as plain text into a Tweet that could be executed in the browser of another user.

We discovered and patched this issue last month. However, a recent site update (unrelated to new Twitter) unknowingly resurfaced it.

Early this morning, a user noticed the security hole and took advantage of it on First, someone created an account that exploited the issue by turning tweets different colors and causing a pop-up box with text to appear when someone hovered over the link in the Tweet. This is why folks are referring to this an “onMouseOver” flaw — the exploit occurred when someone moused over a link.

Other users took this one step further and added code that caused people to retweet the original Tweet without their knowledge.

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