Facebook has addressed a serious vulnerability that could have been exploited by malicious applications to gain access to users’ private photographs.
The security hole was discovered by Laxman Muthiyah, who got a $10,000 reward from Facebook for his findings.
The flaw is related to “photo syncing,” an opt-in feature that allows users to automatically save the photos stored on their mobile phones to a private section in their Facebook account. Users can share these private photos on their Facebook timeline from a desktop computer.
Synced photos should have been private, but the researcher found a vulnerability that allowed third-party Facebook apps to access the files.
According to Muthiyah, the Facebook mobile app accesses the synced content by making a GET request to graph.facebook.com/me/vaultimages with a top level access token. However, before the issue was addressed, Facebook’s servers only checked the owner of the access token and not the application that made the request. This allowed any Facebook application that had been granted access to a user’s photos to read the private content.
The expert said Facebook addressed the issue less than 30 minutes after acknowledging the vulnerability report. The social media giant patched the vulnerability by whitelisting its official mobile applications so that no other apps can access the synced photos.
“That’s hard to argue with – a 30 minute response to a serious privacy flaw is impressive by anybody’s standards,” security expert Graham Cluley wrote on Tripwire’s State of Security blog. “But the fact remains that one has to assume that the flaw has been there on Facebook ever since the photo sync service was introduced in late 2012 – more than two years ago. Although it’s good that Facebook has now resolved the issue, it should never have been there in the first place, or their own researchers should have discovered the problem rather than leaving it for others to uncover.”
This isn’t the first time Muthiyah finds a serious Facebook vulnerability. In February, the researcher reported getting a $12,500 bounty from the company after reporting a Graph API bug that could have been exploited to delete users’ photos. A different flaw, disclosed recently by Lebanon-based researcher Joe Balhis, allowed attackers to delete users’ comments.
Facebook paid out a total of $1.3 million last year through its bug bounty program.