# Mullvad Browser 15.0.21

- Product: Mullvad Browser (https://whatsnew.fyi/product/mullvad-browser)
- Vendor: Mullvad VPN
- Date: 2026-09-03
- Version: 15.0.21
- Original notes: https://github.com/mullvad/mullvad-browser/releases/tag/15.0.21
- Permalink: https://whatsnew.fyi/product/mullvad-browser/releases/15.0.21
- 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** — Updated Firefox to 140.15.0esr
- **changed** — Updated NoScript to 13.6.32.1984
- **changed** — Updated uBlock Origin to 1.74.0
- **fixed** — Websites can no longer initiate a WebSocket connection to a lan/localhost port
- **security** — Backported security fixes from Firefox 155

* All Platforms
   * Updated Firefox to 140.15.0esr
   * Updated NoScript to 13.6.32.1984
   * Updated uBlock Origin to 1.74.0
   * Bug 572: Websites can initiate a WebSocket connection to a lan/localhost port [mullvad-browser]
   * Bug 45259: Backport Security Fixes from Firefox 155 [tor-browser]