I'm having a senior moment here, but wasn't it common to include space in instruction-space and initialized data space, designed to permit binary patching by jump table to (currently) un-used pre-assigned regions?

I thought I'd even seen reference to support in compilers to pre-assign such spaces.

If (for instance) this is a product acquired from outside the Redmond campus, run successfully unpatched since B.C. and now needing work, it might actually be more effective to do what they did instead of reverse-compiling code, re-implementing, the whole shebang.

Security nightmare? Sure. Unsafe? depends. NASA pay old-timers the big bucks to keep things working out in space, which probably involves processes which aren't morally far removed from this.