A Facebook bug allows you to posts messages on friend’s walls that he or she can never delete.
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Here's how it works: Once you’ve blocked a person on Facebook he or she is no longer able to see content that you’ve posted on the social network, including content you’ve posted on that person’s wall. Since the content is no longer visible, it's also not deletable by either party unless the block is removed.
That's clearly noted when you start to block a person on the site "Blocking means you won't be able to see on contact each other of Facebook," however, it's a one-sided agreement that doesn't notify the person being blocked, and leaves all of the content you've posted up to that point still in tact, just not visible to either of you.
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To test the theory, I posted a photo of a Spy Cat on Mashable Business Editor Todd Wasserman’s wall. He was able to see the message when I posted it, however, when I blocked him a few minutes later the image was no longer visible to him or I, but was visible to Christina Warren who was his Facebook friend.
Since you can’t remove what you can’t see, Todd could have potentially never realized a posted the photo in the first place, although it would still be visible to his entire friend base for eternity. He also won’t be able to delete that post from his wall, nor will I unless I decide to unblock him on the site.
While our cat experiment is certainly harmless, the vunerability could certainly be used maliciously, and for posting photo a bit more risqué than a cat looking through some window blinds.
We've reached out to Facebook comment.
This story originally published on Mashable here.