Not my code
No mention of XGKS or PEX. Whew! In the clear. (None of my other X11 stuff ever made it out of IBM, as far as I know. Thank goodness.)
Or to put it another way, apparently no one's bothered doing a security analysis of XGKS or PEX yet...
(I almost want to dig up the XGKS metafile handling source. I have vague memories of fixing - this would have been around '89, I think - various overflows there, but I strongly suspect now that my "fixes" are rather fragile under deliberate attack. Oh well - it's not part of any stock X11 distribution, and probably isn't used much. Though I see Steve Emmerson migrated it to Sourceforge in 2000. Warms the cockles of my heart, that does.)