https://www.mozilla.org/en-US/firefox/91.0.2/releasenotes/

Fixed

• High Contrast Mode is no longer enabled by default when "Increase Contrast" is checked in macOS settings (bug 1726606)

• Firefox no longer clears authentication data when purging trackers, to avoid repeatedly prompting for a password (bug 1721084)

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Available via the internal updater:   Help / About Firefox