Sometimes my reaction to a story is “Wait, are they saying someone was that dumb? … No one could be that dumb! … Oh, gods, they were that dumb!” Naked Security’s account of the Zip Slip vulnerability is just such a story.
The article starts with a fair warning that the vulnerability is “so simple you’ll need to put a cushion on your desk before you read any further (in case of involuntary headdesk injury).” It explains that because of the coding mistake called “Zip Slip,” “attackers can create Zip archives that use path traversal to overwrite important files on affected systems, either destroying them or replacing them with malicious alternatives.” This is where I started to suspect.
The vulnerability isn’t in the Zip format as such, but in bad coding found in some of the zillion ad hoc pieces of software written to unpack Zip files. Have you figured it out yet? I’ll put the cut here to give you a chance to think…