Industry News

Yahoo flaw allowed others read your emails, until now

Yahoo fixed an XSS flaw that allowed hackers to read any user’s email by simply sending a new email, according to news reports.

The bug, reported by a Finish researcher, affected Yahoo’s email HTML filtering system. Yahoo filters HTMLs to prevent malicious code from executing in the web browser. However, if you embedded the link of a reputable site, Yahoo wouldn’t pay much attention to it.

Using this insight, Jouko Pynnonen sent an email with different kinds of attachments to inspect the “raw” HTML of that email.

“As long as the URL pointed to a white-listed website such as YouTube, it was not further sanity checked or encoded,” a blog post detailing the research reads.

This means an attacker could send an email with malicious JavaScript code and it would automatically execute.

The attack required the victim to view an email sent by the attacker,” the researcher says. “No further interaction (such as clicking on a link or opening an attachment) was required.”

The flaw was patched on Nov. 29 as a result of Yahoo’s bug bounty program, and the white hat hacker was rewarded with $10,000.

Last year, Jouko Pynnonen reported another serious Yahoo flaw that allowed an attacker to take over any user’s account by using XSS vulnerability.


About the author

Alexandra GHEORGHE

Alexandra started writing about IT at the dawn of the decade - when an iPad was an eye-injury patch, we were minus Google+ and we all had Jobs. She has since wielded her background in PR and marketing communications to translate binary code to colorful stories that have been known to wear out readers' mouse scrolls. Alexandra is also a social media enthusiast who 'likes' only what she likes and LOLs only when she laughs out loud.