I've received a couple of suggestions, thanks, but none seem right. BTW, I'm sorry (Liam) that I didn't make it clearer that it was absolutely a software bug, which excludes Spectre, Rowhammer, Meltdown. Aside: the Meltdown and/or Spectre patch to macOS hurt performance ... the elapsed time to compile 500 programs increased by about 12%. (At the time of the patch, I tested (properly) before and after the patch ... then forgot to publish, and since misplaced my notes.) Although I mentioned 'code', I should have been more specific: C (or, possibly, C++), but definitely no other language. I don't recall it being a buffer overflow. I *think* it was some kind of authentication failure (e.g., incorrectly reporting "ok"), but I'm not sure. I do know I wrote a several page article about it, and how certain coding practices led to it, but I can't *find* the article now :( (not published) My guess of 4-6 years ago is possibly narrower than it should be, but I'm not sure. My hope is that by being reminded of the vulnerability name, I can search my computer, and backups, for text files containing that name :) (Or the name of function associated with the problem.) thanks, Stan