CVE-2026-54090: File Browser has a Command Execution Allowlist Bypass via Shell Metacharacter Injection

When a shell interpreter is configured (e.g. /bin/sh -c), the command allowlist can be bypassed through shell metacharacters. The allowlist validates only the first token of user input, but the entire raw string is handed to the shell — semicolons, pipes, backticks, and $() all work to chain arbitrary commands after a permitted one.

This is a distinct issue from CVE-2025-52995 (regex partial matching, fixed in 2.33.10) and CVE-2025-52903 (GTFOBins-style subcommands). The slices.Contains fix does not prevent this bypass.