GHSA-G9XF-7F8Q-9MCJ pypdf: Possible infinite loop when processing threads/articles in writer

Impact An attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires merging a file with threads/articles into a writer. Patches This has been fixed in pypdf==6.13.1. Workarounds If users cannot upgrade yet, consider applying the changes from PR 3839...