# What changed in flask

> 1 change in flask 3 from its official release notes, upgrade guides and advisories: 1 security. Each one cited. Sources checked 2026-10-27. HTML: https://unstale.sh/pypi/flask/

To see which of these apply to a repository, run `npx @unstale/cli init` in it.

## flask 3

### Security

- Operations that access keys without accessing values, such as `in` and `len`, now mark the session as accessed. (3.1.3) — [release notes](https://github.com/pallets/flask/releases/tag/3.1.3), [security advisory](https://github.com/advisories/GHSA-68RP-WP8R-4726)