Paper is pre-1.0. Security fixes are applied to the latest released minor version only; there are no long-term support branches.

Please do not open a public issue for a security problem.

Report it through GitHub's private vulnerability reporting: Report a vulnerability.

If that is unavailable to you, open a regular issue containing only the words "security report — please contact me" and no technical detail, and a maintainer will arrange a private channel.

Please include, as far as you can:

• the affected version or commit,
• a minimal input that reproduces the problem (PDF, HTML, SVG, or font file),
• what an attacker gains, and
• any suggested fix.

You can expect an acknowledgement within 7 days and a status update at least every 14 days until the report is resolved.

Paper parses untrusted input: HTML, CSS, SVG, images, fonts, and existing PDF files. The following are in scope:

• memory-safety failures reachable from parsed input: panics, unbounded allocation, unbounded recursion, or non-termination,
• escaping the asset sandbox — reading a file outside the configured base directory via WithImageBaseDir / WithStylesheetBaseDir,
• outbound requests to hosts a caller did not authorise, bypassing the WithRemoteAssets opt-in and its URLPolicy,
• defects in PDF encryption or signing that weaken the protection a caller asked for.

The following are not vulnerabilities in Paper:

• MD5 and RC4 in the PDF standard security handler, and SHA-1 in PAdES VRI keys. These algorithms are named by ISO 32000-1 §7.6.3 and ETSI EN 319 142; they are what the formats specify, not a choice this library makes.
• Reading a path a caller passed in directly (LoadPNG, Pdf.Save, AddUTF8Font, tmpl.Render). Opening the caller's path is the documented purpose of those functions.
• Resource exhaustion from input a caller supplies to itself, where a documented limit exists and was not configured (see WithHTMLLimits).

• govulncheck runs in CI on every push and on a weekly schedule.
• Fuzz targets cover the untrusted-input parsers and run in CI.
• Untrusted asset paths are resolved through os.Root, which refuses absolute paths and any path escaping the configured base directory.
• Workflow actions are pinned to commit SHAs.