This post has been updated since it was originally published.

Update: Facebook explained in a statement that the spam attack was the result of a browser vulnerability that tricked users into running malicious script and sharing the content on their own profiles.

The images on the site are so disturbing that some users say they are threatening to leave the site. Users have reported seeing images of dead animals and altered images of celebrities in explicit situations.

“I am so close to just deactivating my facebook account because of these hackers,” wrote one Twitter user, just one of many who have threatened to leave the network because of the attacks.

Original Post:Facebook users have been reporting a flood of violent and pornographic images invading their news feeds, prompting the social network to launch an investigation into what appears to be a widespread spam or hacking attack.

Users started reporting the images in their accounts a few days ago, ZDNet reported, but many more people began reporting the images on Monday night.

In a statement, Facebook spokesman Andrew Noyes said the company is looking into the attacks.

“Protecting the people who use Facebook from spam and malicious content is a top priority for us and we are always working to improve our systems to isolate and remove material that violates our terms,” he said. “We have recently experienced an increase in reports and we are investigating and addressing the issue.”

Graham Cluley of the security company Sophos said on a company blog that he is hearing reports that users whose accounts post the images are unable to see them on their own news feeds.

There are several theories floating around about what exactly may be happening to cause the images to appear. It’s possible that the images are the result of a Facebook scam, in which users click a link and open up their accounts to viruses that can post whatever hackers want to users’ profiles.

Another theory is that a splinter group of Anonymous made good on its threat to put out a virus to “take down Facebook,” in an attack planned for Guy Fawkes Day, Nov. 5, but there’s been no indication of that group taking credit for the attack.

(Washington Post Co. chairman and chief executive Donald E. Graham is a member of the Facebook board of directors.)

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