
Added a font sanity check to avoid triggering a potential vulnerability on unpatched Windows operating systems (related to CVE-2021-24093). Added required interaction with file/folder open dialog boxes on html file input elements on some operating systems to avoid malicious content tricking users into uploading sensitive files unintentionally (related to CVE-2021-23956). Disabled AV1 codec use by default again since our implementation has significant streaming issues (particularly audio) that needs further work. Fixed a full browser deadlock when page scripting would flood browsing history with rapid location state changes. This could make certain login procedures fail to work. Fixed a regression where AES-GCM in WebCrypto ("subtle" crypto API) wasn't working. Fixed a regression where changes to useragent compatibility required a restart to take effect.

Further improved support for building on FreeBSD. Improved performance of JSON stringify. Updated the lz4 library for performance and security updates. Updated some site-specific user-agent overrides for web compatibility. Updated the wording and inclusion of more select license blocks in about:license.

Implemented numeric separators in javascript. Implemented well-formed JSON stringify.

Language packs for the following newly-supported languages:
