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.