zipcheck is a static risk scanner. It reads archive metadata and reports whether extraction is likely to be dangerous. It is not a sandbox, an antivirus, or a guarantee that an archive is safe.

The scanner itself is designed to be safe against hostile inputs:

• it never extracts archive members to disk; decrypted ZIP data is counted or held in a bounded in-memory image only;
• it never invokes unzip, 7z, tar, rar, or any external program;
• it caps metadata reads, entry counts, nested depth, decrypted bytes and wall-clock time;
• it checks 7z/xz decoder dictionary sizes against a memory cap;
• it keeps a supplied ZIP password out of findings, notes, JSON and Limits representations, and never writes it anywhere.

Those controls protect against resource exhaustion during the scan. They say nothing about what happens if you later extract the archive with another tool. Always extract untrusted archives in a disposable environment with disk, CPU, memory and time quotas.

Security fixes are applied to the latest 0.3.x release.

Please do not attach a live archive bomb to a public issue. Instead:

1. Open a private GitHub security advisory for the repository.
2. Describe the problem and the smallest possible reproduction: a hex dump, a generator snippet, or a metadata-only fixture. A 50-byte file that declares a huge size is usually enough.
3. Include the version, Python version and operating system.

Useful reports include:

• a malformed archive that crashes, hangs or allocates unbounded memory;
• a bounded-decompression bypass that exceeds the documented caps;
• a parser confusion that makes a clearly dangerous archive report clean;
• path traversal or command execution (there should be none);
• a way to make the scanner write to disk or spawn a process;
• a way to make a supplied password appear in output, logs or process metadata beyond the documented --password argv caveat.

• Brute-forcing, guessing or recovering passwords.
• Decrypting password-protected 7z/RAR data or encrypted RAR headers. ZIP encryption is supported when a password is supplied and, for AES, the optional pyzipper extra is installed.
• Proving that an archive is benign. clean means "no rule fired", not "safe".
• Detecting bombs in formats that are not parsed.
• Protecting a machine from extraction performed by a different program.

The repository's tests build metadata-only archives that are tiny on disk. The optional tools/generate_samples.py creates real bombs; run it only inside a VM/container, never on a workstation, and never extract its output.