backintime (aka Back in Time) before 1.1.24 did improper escaping/quoting of file paths used as arguments to the 'notify-send' command, leading to some parts of file paths being executed as shell commands within an os.system call in qt4/plugins/notifyplugin.py. This could allow an attacker to craft an unreadable file with a specific name to run arbitrary shell commands.

The _checkPolkitPrivilege function in serviceHelper.py in Back In Time (aka backintime) 1.1.18 and earlier uses a deprecated polkit authorization method (unix-process) that is subject to a race condition (time of check, time of use). With this authorization method, the owner of a process requesting a polkit operation is checked by polkitd via /proc/<pid>/status, by which time the requesting process may have been replaced by a different process with the same PID that has different privileges then the original requester.