11.0.1

Security

• Fixed a path traversal in the failure report sample filenames written by --output (GHSA-c284-w5m6-jhjm, affects 9.0.6 through 11.0.0). save_output() named each failure report's message sample after the sample's Subject header, falling back to the raw, unsanitized subject whenever sanitizing it produced an empty string. A subject consisting only of path separators and dots — ../../../ or / — sanitizes to nothing, so the raw value reached os.path.join() and the .eml file was written outside the samples directory, or at an absolute path. The subject comes from a message that failed authentication, so anyone who can send mail to a monitored mailbox controls it. The filename is now sanitized at write time and falls back to sample, and the filename_safe_subject key that a library caller may supply alongside the subject is no longer trusted.
• Fixed unbounded decompression of report attachments (GHSA-43qf-f35w-2x4r, affects all versions through 11.0.0). extract_report() inflated gzip and zip attachments with no limit on the output size. The attachment's content is chosen by whoever sent it, and deflate reaches compression ratios of about 1000:1 on degenerate input, so a 100 KB attachment from any sender a monitored mailbox accepts inflated to 100 MB, with a peak of about twice that. Extraction now stops at 100 MiB of decompressed data and raises ParserError. The limit is deliberately not configurable: real DMARC aggregate, failure, and SMTP TLS reports are orders of magnitude smaller.

Bug fixes

• CSV output (failure.csv, and the other CSV renderers) no longer raises _csv.Error on Python 3.10 when a report field contains a NUL character. Python 3.10's csv writer rejects any field containing NUL unless an escapechar is set (CPython issue 97503, a 3.10 regression fixed in 3.11+). Failure report text fields (subject, user agent, authentication results, addresses, and more) come from untrusted mail, so a NUL byte anywhere in one made parsed_failure_reports_to_csv() — and therefore save_output() — raise on 3.10, uncaught by the CLI's except (OSError, ValueError) around save_output. The character is now stripped from CSV fields on every Python version, matching the sanitizing already applied to sample filenames.