# mitmproxy v12.2.3 — mitmproxy 12.2.3

- Product: mitmproxy (https://whatsnew.fyi/product/mitmproxy)
- Vendor: mitmproxy
- Date: 2026-05-12
- Version: v12.2.3
- Original notes: https://github.com/mitmproxy/mitmproxy/releases/tag/v12.2.3
- Permalink: https://whatsnew.fyi/product/mitmproxy/releases/v12.2.3
- Labels: Platforms: Desktop

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

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- **changed** — Reduce generated leaf certificate validity from 199 to 197 days so the 2-day notBefore backdate remains below Chromium's 200-day limit
- **fixed** — Fix a bug where mitmweb would not pick up its XSRF cookie
- **fixed** — Fix authority and subject key identifier mismatch errors when mitmproxy is configured with a custom CA whose SubjectKeyIdentifier was not derived as SHA-1 of the public key
- **fixed** — Fix IndexError in is_mostly_bin when exporting flows to HAR with payloads that have a UTF-8 continuation byte at the 100-byte cutoff

- Reduce generated leaf certificate validity from 199 to 197 days so the 2-day
  `notBefore` backdate remains below Chromium's 200-day limit.
  ([#8203](https://github.com/mitmproxy/mitmproxy/pull/8203), @emanuele-em)
- Fixed a bug where mitmweb would not pick up its XSRF cookie.
  ([#8224](https://github.com/mitmproxy/mitmproxy/pull/8224), @mhils)
- Fix `authority and subject key identifier mismatch` errors when mitmproxy
  is configured with a custom CA whose SubjectKeyIdentifier was not derived
  as SHA-1 of the public key.
  ([#8214](https://github.com/mitmproxy/mitmproxy/pull/8214), @unique-jakub)
- Fix `IndexError` in `is_mostly_bin` when exporting flows to HAR with payloads
  that have a UTF-8 continuation byte at the 100-byte cutoff.
  ([#8196](https://github.com/mitmproxy/mitmproxy/pull/8196), @juliosuas)