CVE-2026-54540: Pheditor has an authenticated terminal command whitelist bypass

Pheditor 2.0.4 has an authenticated terminal command whitelist bypass.

The terminal feature checks whether the submitted command starts with one of the configured TERMINAL_COMMANDS values, then passes the full command string to shell_exec(). Shell command substitution such as $() is not blocked, so an authenticated user with the terminal permission can bypass a restricted command allowlist and execute arbitrary shell commands as the web server user.