Feeds

Facebook caught exposing millions of user credentials

App bug overrides user privacy settings

Seven Steps to Software Security

Facebook has leaked access to millions of users' photographs, profiles and other personal information because of a years-old bug that overrides individual privacy settings, researchers from Symantec said.

The flaw, which the researchers estimate has affected hundreds of thousands of applications, exposed user access tokens to advertisers and others. The tokens serve as a spare set of keys that Facebook apps use to perform certain actions on behalf of the user, such as posting messages to a Facebook wall or sending RSVP replies to invitations. For years, many apps that rely on an older form of user authentication turned over these keys to third parties, giving them the ability to access information users specifically designated as off limits.

The Symantec researchers said Facebook has fixed the underlying bug, but they warned that tokens already exposed may still be widely accessible.

“There is no good way to estimate how many access tokens have already been leaked since the release [of] Facebook applications back in 2007,” Symantec's Nishant Doshi wrote in a blog post published on Tuesday. “We fear a lot of these tokens might still be available in log files of third-party servers or still being actively used by advertisers.”

While many access tokens expire shortly after they're issued, Facebook also supplies offline access tokens that remain valid indefinitely. Facebook users can close this potential security hole by changing their passwords, which immediately revokes all previously issued keys.

The flaw resides in an authentication scheme that predates the roll out of a newer standard known as OAUTH. Facebook apps that rely on the legacy system and use certain commonly used code variables will leak access tokens in URLs that are automatically opened by the application host. The credentials can then be leaked to advertisers or other third parties that embed iframe tags on the host's page.

“The Facebook application is now in a position to inadvertently leak the access tokens to third parties potentially on purpose and unfortunately very commonly by accident,” Doshi wrote. “In particular, this URL, including the access token, is passed to third-party advertisers as part of the referrer field of the HTTP requests.”

A Facebook spokeswoman said there is no evidence the weakness has been exploited in ways that would violate the social network's privacy policy, which steadfastly promises: “We never share your personal information with our advertisers.” Facebook on Tuesday also announced it was permanently retiring the old authentication routine.

Doshi, who was assisted by fellow researcher Candid Wueest, said there's no way to know precisely how many apps or Facebook users were affected by the glitch. They estimate that as of last month, almost 100,000 applications were enabling the leakage and that over the years “hundreds of thousands of applications may have inadvertently leaked millions of access tokens to third parties.”

Facebook over the years has regularly been criticized for compromising the security of its users, which now number more than 500 million. The company has rolled out improvements, such as always-on web encryption, although users still must be savvy enough to turn it on themselves, since the SSL feature isn't enabled by default.

As indicated above, all previously issued access tokens can be cleared by changing your Facebook password. Readers who aren't sure if they're affected might want to err on the side of security and update their password now. ®

Mobile application security vulnerability report

More from The Register

next story
Yorkshire cops fail to grasp principle behind BT Fon Wi-Fi network
'Prevent people that are passing by to hook up to your network', pleads plod
HIDDEN packet sniffer spy tech in MILLIONS of iPhones, iPads – expert
Don't panic though – Apple's backdoor is not wide open to all, guru tells us
Mozilla fixes CRITICAL security holes in Firefox, urges v31 upgrade
Misc memory hazards 'could be exploited' - and guess what, one's a Javascript vuln
BMW's ConnectedDrive falls over, bosses blame upgrade snafu
Traffic flows up 20% as motorway middle lanes miraculously unclog
LibreSSL RNG bug fix: What's all the forking fuss about, ask devs
Blow to bit-spitter 'tis but a flesh wound, claim team
Manic malware Mayhem spreads through Linux, FreeBSD web servers
And how Google could cripple infection rate in a second
Don't look, Snowden: Security biz chases Tails with zero-day flaws alert
Exodus vows not to sell secrets of whistleblower's favorite OS
Researcher sat on critical IE bugs for THREE YEARS
VUPEN waited for Pwn2Own cash while IE's sandbox leaked
prev story

Whitepapers

Designing a Defense for Mobile Applications
Learn about the various considerations for defending mobile applications - from the application architecture itself to the myriad testing technologies.
How modern custom applications can spur business growth
Learn how to create, deploy and manage custom applications without consuming or expanding the need for scarce, expensive IT resources.
Reducing security risks from open source software
Follow a few strategies and your organization can gain the full benefits of open source and the cloud without compromising the security of your applications.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.
Consolidation: the foundation for IT and business transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.