A flaw was found in all versions of ghostscript 9.x before 9.28,
where the `.charkeys` procedure, where it did not properly secure
its privileged calls, enabling scripts to bypass `-dSAFER` restrictions.
An attacker could abuse this flaw by creating a specially crafted
PostScript file that could escalate privileges within the Ghostscript
and access files outside of restricted areas or execute commands.
