Problem: tests: no test for using shellescape() in combination with :!
Solution: Add a test that checks runtime files for using wrong
combination of shellescape() with ! ex command
This has lead to a few security relevant issues, so add a test that
checks all runtime files for any ! followed by a shellescape() that does
not use the {special} arg.
related: Commit: 3fb5e58fbc63d86a3e65f1a141b0d67af2 (patch 9.2.0479:
[security]: runtime(tar): command injection in tar plugin)
closes: vim/vim#20286
Supported by AI
https://github.com/vim/vim/commit/fccc2adc98c3d6664f1f2d8ddab17b096e647986
Co-authored-by: Christian Brabandt <cb@256bit.org>
