Facebook probes bug that creates 'undeletable' wall posts

Facebook is now investigating a possible bug that allows users to post messages on their friends' walls that cannot be deleted, a tech site said this week. Mashable said this applies to situations where a user blocked a friend – but content the user previously posted can still be seen by the blocked person's friends. "The person being blocked isn’t notified, and all of the content you’ve previously posted on their wall remains intact but invisible to both of you," Mashable's Emily Price said. "Facebook is currently investigating the issue," Price added. Price said this was due to Facebook's mechanism, where once a user blocks a Facebook friend, the blocked friend can no longer see what the blocker posts on Facebook, including posts the blocker made on the blocked friend's wall. But since the content is no longer visible even to the blocker, it can no longer be deleted. "The only way either party can see the post again is if the block is removed," Mashable said. Price tested the theory by posting a photo of a Spy Cat on a colleague's wall. He was able to see the message. She then blocked him some minutes later, and the image she posted was no longer visible to her and her blocked colleague. However, the message was still visible to an unblocked Facebook friend of her blocked colleague. "Since you can’t remove what you can’t see, (the blocked friend) could have potentially never realized I posted the photo in the first place, although it would still be visible to his entire friend base for eternity. He also wouldn’t be able to delete the post from his wall, nor will I unless I decide to unblock him on the site," Price said. Price warned the potential vulnerability could be exploited maliciously by someone using a photo "a bit more risqué than a cat looking through some window blinds." — LBG, GMA News