Report privately, not through the public issue tracker:

• Preferred: GitHub's private vulnerability reporting, from the repository's Security tab.
• Alternative: email libraz@libraz.net.

Include the document that triggers it, what happened, the affected version and package, and a minimal reproduction if you have one. Expect an acknowledgement within a few days.

Pre-1.0. Fixes land on the latest release only; older versions are not patched.

mejiro lays out text it did not write and opens EPUB files it did not produce, so the parsing path is the interesting surface. In scope:

• An EPUB that escapes the extraction directory through a crafted entry path, or that expands to an unreasonable size from a small archive.
• Markup inside a document reaching the DOM as script or as an active URL through the reader and editor components, rather than as text.
• Text, ruby markup or an exclusion region that causes a hang or unbounded memory growth in the layout engine.
• External entity resolution or entity expansion while parsing a document's XML.
• Any network access made while opening a local document.

• Wrong typesetting. A line broken in the wrong place, misapplied kinsoku or misaligned ruby is a correctness bug; report it as a normal issue.
• Documented limits behaving as documented — document-size and iteration ceilings exist so a hostile file cannot exhaust the host. A ceiling that can be bypassed is in scope.
• Content an application deliberately passed through after disabling sanitisation.
• Findings that require an attacker to already control the process embedding the engine.