Koha is vulnerable to OS command injection in the Task Scheduler deletion path. The tools/scheduler.pl handler accepts the jobid request parameter for op=cud-delete and passes it to C4::Scheduler::remove_at_job without validating it. Schedule::At::remove substitutes the supplied job ID into an atrm command string without quoting or escaping it and executes the command through a single-argument system() call, which invokes the shell. An authenticated staff user with the tools => schedule_tasks permission can therefore execute arbitrary operating-system commands as the Koha web/application user by supplying shell metacharacters in jobid. The issue is fixed in Koha 24.11.20, 25.05.15, 25.11.09, and 26.05.04, and in the 26.11 development branch.