“We have already resolved these security issues,” a Zoom spokesperson told WIRED in a statement. In other words, Wardle found that he could change the name of the software he was trying to sneak through to contain the markers Zoom was broadly looking for and get the malicious package past Zoom’s signature check. Zoom’s signature check was essentially looking at everything on the table and accepting the random birthday card signature instead of actually checking whether the signature was in the right place on the right document. Imagine that you carefully sign a legal document and then put the piece of paper facedown on a table next to a birthday card that you signed more casually for your sister.

Ultimately, he realized that Zoom’s check could be defeated. (It’s a sort of wax-seal check to confirm the integrity and provenance of software.) Wardle knew from past research and his own software development that it can be difficult to truly validate signatures in the types of conditions Zoom had set up. The first vulnerability Wardle found, though, was in the cryptographic signature check.

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