Instagram is a free photo-sharing program that allows users to take a photo and apply a digital filter to alter the image. According to Guerrero, a lack of control logic used to process the approval process for requests for friendship meant that an attacker could launch a brute force attack and be added as a "friend" to any account.
"Being able to access images taken by users of the application and the information posted on their profile," the researcher explained in a blog post. "Also, it was found that this vulnerability also affects users whose album is private, allowing access to photos stored on it."
Guerrero posted a proof-of-concept attack exploiting the issue on his blog, adding himself to a group of people being followed by Facebook CEO Mark Zuckerberg and sending him a message.
"Just give us a tour of the Hollywood celebrity twitter, celebrities, presidents, government, etc.," he blogged. "Access your profile Instagram, get your user ID and automatically exploit this vulnerability. Whether your profile private, we get access to your photos."
According to Instagram, however, the bug did not actually put users' data at risk.
"We don't have any evidence that this bug was taken advantage of at any other scale than very minimal experiments by a technical researcher," the company says, adding that private photos were never made public -- a statement that seems to contradict Guerrero's findings.
Instagram was purchased by Facebook earlier this year. Whether Facebook will face any sanctions for this vulnerability remains to be seen, blogged ESET security evangelist Stephen Cobb.
"One suspects that the Federal Trade Commission will take a look at the matter, given that Facebook is already subject to a 20-year FTC settlement over false claims about protecting the privacy of its users," he noted.
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