Sometimes all it takes to root out a new software vulnerability is to study and analyze previous bug reports. That’s how researcher Csaba Fitzl says he sniffed out some new Apple macOS vulnerabilities, one of which was a mirror image of a logic flaw that a group of researchers competing in the 2020 Pwn2Own contest found and executed there.

Fitzl, a content developer for Offensive Security, says he reread and studied the winning six-exploit chain that the researchers used to hack macOS. One of the exploits in that chain weaponized a privilege escalation bug, which Apple later fixed.