Revert CVE-2018-12270 back to check

Marking it as NFU as per "Valve Steam" was defintively prematurely,
there is for instance src:steam in the archive which might be impacted
by the issue.

The CVE description and references are unfortunately not enlightening
regarding if src;steam might be affected.

Cf. https://github.com/VixusFoxy/CVE/wiki/CVE-2018-12270