[ozzy47]

I would think the use of the attachment manager would prevent that "image" from even uploading. It should cause an error message that says something like, "not a recognized image format." It also would not be in the format of , it would have to be in [ attach]1234567[/attach].

If it is posted between tags, then you could prevent it by censoring the term base64. Adding that to the censored words list will break the image and cause either nothing to appear in some browsers or a red X to appear in others.