(1) bash before 1.14.7, and (2) tcsh 6.05 allow local users to gain privileges via directory names that contain shell metacharacters (` back-tick), which can cause the commands enclosed in the directory name to be executed when the shell expands filenames using the \w option in the PS1 variable.
https://github.com/IlyaTrihkin/linux-audit-engine
https://euvd.enisa.europa.eu/vulnerability/EUVD-1999-1364