[Security] Arbitrary file write via path traversal in output_directory parameter

[Correctover]

Summary

The build_output_path() function in utils.py accepts a user-controlled output_directory parameter without validating that the resulting path stays within the intended base directory. An attacker can write arbitrary files to any writable location on the filesystem.

Details

File: minimax_mcp/utils.py, function build_output_path()

if output_directory is None:
    output_path = Path(os.path.expanduser(base_path))
elif not os.path.isabs(os.path.expanduser(output_directory)):
    output_path = Path(os.path.expanduser(base_path)) / Path(output_directory)
else:
    output_path = Path(os.path.expanduser(output_directory))  # No confinement!

Impact

An attacker can write arbitrary files to any writable location (overwrite cron jobs, plant backdoors, write SSH keys).

Suggested Fix

output_path = Path(os.path.expanduser(output_directory)).resolve()
base_resolved = Path(os.path.expanduser(base_path)).resolve()
if not str(output_path).startswith(str(base_resolved)):
    raise MinimaxMcpError("Output path escapes base directory")

Reported by Correctover Security Research (https://correctover.com)