Ahmed Aboul-Ela wrote on his blog that he and a fellow researcher, Ibrahim Mosaad, wanted to find a problem in a feature on YouTube "that not many bug hunters have tested."
They focused on a setting in YouTube that holds comments for review before they're published. If that feature is enabled, comments are then listed in a control panel labeled "held for review."
Aboul-Ela wrote he intercepted the http request that is sent to Google when a comment is approved. The request contains two parameters: "comment_id" and "video_id."
An error is returned if the video_id is changed to a different one, he wrote. But YouTube accepted changing the content_id number to a different video, which then caused the comment to get copied to that video.
"The original comment from the original video doesn't get removed, and the author of the comment does not get notified that his comment is copied onto another video," Aboul-Ela wrote.
The flaw could have been used in many ways. It could be used to make it appear that a video is more popular that it actually is. Or it could have been used to falsely make it appear a celebrity or public figure commented on something, Aboul-Ela wrote.
Google fixed the vulnerability within a week of being notified on March 25 and paid a US$3,133.70 bug bounty.
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