A New Facebook Bug Exposes Millions of Email Addresses

Still smarting from last month’s dump of phone numbers belonging to 500 million Facebook users, the social media giant has a new privacy crisis to contend with: a tool that, on a massive scale, links Facebook accounts with their associated email addresses, even when users choose settings to keep them from being public. Wired reports: A video circulating on Tuesday showed a researcher demonstrating a tool named Facebook Email Search v1.0, which he said could link Facebook accounts to as many as 5 million email addresses per day. The researcher — who said he went public after Facebook said it didn’t think the weakness he found was “important” enough to be fixed — fed the tool a list of 65,000 email addresses and watched what happened next. “As you can see from the output log here, I’m getting a significant amount of results from them,” the researcher said as the video showed the tool crunching the address list. “I’ve spent maybe $10 to buy 200-odd Facebook accounts. And within three minutes, I have managed to do this for 6,000 [email] accounts.”

The researcher […] said that Facebook Email Search exploited a front-end vulnerability that he reported to Facebook recently but that “they [Facebook] do not consider to be important enough to be patched.” Earlier this year, Facebook had a similar vulnerability that was ultimately fixed. “This is essentially the exact same vulnerability,” the researcher says. “And for some reason, despite me demonstrating this to Facebook and making them aware of it, they have told me directly that they will not be taking action against it.”

In a statement, Facebook said: “It appears that we erroneously closed out this bug bounty report before routing to the appropriate team. We appreciate the researcher sharing the information and are taking initial actions to mitigate this issue while we follow up to better understand their findings.” A Facebook representative didn’t respond to a question asking if the company told the researcher it didn’t consider the vulnerability important enough to warrant a fix. The representative said Facebook engineers believe they have mitigated the leak by disabling the technique shown in the video.