The Windows search path landed in 82a9052 wraps shell args in cmd.exe-
level "powershell -Command \"...'%s'...\"". PowerShell's single quotes
hold the inner '%s' interpolation, but a literal " inside the user-
supplied value can close the cmd.exe outer quote. With ' ; | & $ `
already blocked, that wouldn't reach RCE on its own — but < and > were
unblocked, so a quote-break followed by cmd.exe redirection (e.g.
*">C:\evil.txt") would expose a file-write primitive.
Block " < > unconditionally. The validator's contract is "safe inside
single quotes for shell interpolation"; on POSIX these aren't strictly
necessary (single quotes hold), but on Windows the cmd.exe→powershell
wrapping makes them load-bearing, and unconditional blocking keeps the
validator simple — no ifdef-laddered policy and no surprises if a future
caller invokes it from a different shell context.
Three tests added to tests/test_security.c covering each new char.
Martin Vogel