A recently patched vulnerability in text editors preinstalled in a variety of Linux distributions allows hackers to take control of computers when users open a malicious text file. The latest version of Apple’s macOS is continuing to use a vulnerable version, although attacks only work when users have changed a default setting that enables a feature called modelines.

Vim and its forked derivative, NeoVim, contained a flaw that resided in modelines. This feature lets users specify window dimensions and other custom options near the start or end of a text file. While modelines restricts the commands available and runs them inside a sandbox that’s cordoned off from the operating system, researcher Armin Razmjou noticed the source! command (including the bang on the end) bypassed that protection.