git-fastclone before 1.0.5 passes user modifiable strings directly to a shell command. An attacker can execute malicious commands by modifying the strings that are passed as arguments to "cd " and "git clone " commands in the library.
https://github.com/advisories/GHSA-mf6w-45cf-qhmp
https://hackerone.com/reports/105190
https://github.com/square/git-fastclone/pull/5