phpoffice/phpspreadsheet: technical due diligence, read from its repository

The median source file here is 66 lines. 20 files exceed 1,000 lines, the largest being 4,923. Size is not a defect on its own — some problems genuinely live in one place — but these are where merge conflicts, review fatigue and single-owner knowledge concentrate, and they are the first thing that slows an inheriting engineer down.

4 third-party CI actions are referenced by a tag or branch rather than a commit, so they run whatever that tag points to on the day. Tags have been moved to malicious commits in real supply-chain attacks, and a piped script is whatever the server returns that minute. Pinning to a commit is the fix, and it is small.

2 places read data with a deserialiser that executes what it reads (PHP `unserialize`). That is safe on data the system wrote itself and remote code execution on anything else. Ask where each one's input comes from.

The root licence changed 1 time(s). Code taken under earlier terms stays under them; check which terms any fork or customer relied on.

The newest was published on 2026-10-12. A project that publishes advisories is telling its users about its fixes, and the count and pace say how much security work it carries. None of them affects the surveyed version. The record is incomplete: NVD: 2 records name PhpSpreadsheet with nothing tying them to this repository (CVE-2025-58051, CVE-2026-86020).