Same thing could/would happen with an open source harness.
> Often Claude commits the file itself. In 539 of the 1,105 repos with a real secret that we traced, a commit co-authored by Claude changed the file. Those commits name every recent model, from Sonnet 4.5 to Opus 5.5.
Could open source harnesses do that? Sure, if they were programmed in a similar fashion as Claude Code. Do you have any evidence of it happening?
None of this has anything to do with open vs. closed source.
Humans do it!