- Authentication using a query string is now deprecated, as per [MSC4126](https://github.com/matrix-org/matrix-spec-proposals/issues/4126). The `Authorization` header should be used instead. ([#1808](https://github.com/matrix-org/matrix-spec/issues/1808))
- Use of the `/_matrix/media/*` endpoints is now deprecated. New, authenticated, endpoints are available instead. ([#1858](https://github.com/matrix-org/matrix-spec/issues/1858))
- Add support for muting in VoIP calls, as per [MSC3291](https://github.com/matrix-org/matrix-spec-proposals/pull/3291). ([#1755](https://github.com/matrix-org/matrix-spec/issues/1755))
- Add optional `animated` query string option to `GET /thumbnail`, as per [MSC2705](https://github.com/matrix-org/matrix-spec-proposals/pull/2705). ([#1757](https://github.com/matrix-org/matrix-spec/issues/1757))
- Specify terms of services at registration, as per [MSC1692](https://github.com/matrix-org/matrix-spec-proposals/pull/1692). ([#1812](https://github.com/matrix-org/matrix-spec/issues/1812))
- Add support for mathematical messages, as per [MSC2191](https://github.com/matrix-org/matrix-spec-proposals/pull/2191). ([#1816](https://github.com/matrix-org/matrix-spec/issues/1816))
- Do not require UIA when first uploading cross-signing keys, as per [MSC3967](https://github.com/matrix-org/matrix-spec-proposals/pull/3967). ([#1828](https://github.com/matrix-org/matrix-spec/issues/1828))
- Add the new `unsigned.membership` property to events, as per [MSC4115](https://github.com/matrix-org/matrix-spec-proposals/pull/4115). ([#1847](https://github.com/matrix-org/matrix-spec/issues/1847))
- Media downloads and thumbnails are now authenticated, as per [MSC3916](https://github.com/matrix-org/matrix-spec-proposals/pull/3916). ([#1858](https://github.com/matrix-org/matrix-spec/issues/1858))
- Some media endpoints are now consistently under `/_matrix/client/{version}/media/*` instead of `/_matrix/media/*`, as per [MSC3916](https://github.com/matrix-org/matrix-spec-proposals/pull/3916). ([#1858](https://github.com/matrix-org/matrix-spec/issues/1858))
**Spec Clarifications**
- Add `/logout` and clarify the endpoints which do not take a JSON request body. ([#1644](https://github.com/matrix-org/matrix-spec/issues/1644))
- Clarify that the `type` of the `POST /login` request must be one of the types returned by the `GET /login` response. ([#1776](https://github.com/matrix-org/matrix-spec/issues/1776))
- Link to existing grammar where possible in types. ([#1813](https://github.com/matrix-org/matrix-spec/issues/1813))
- Rename "recovery key" to "backup decryption key". ([#1819](https://github.com/matrix-org/matrix-spec/issues/1819))
- Clarify that the device's Ed25519 signing key should be used in QR code verification (as opposed to the device's Curve25519 identity key). ([#1829](https://github.com/matrix-org/matrix-spec/issues/1829))
- Fix various typos throughout the specification. ([#1832](https://github.com/matrix-org/matrix-spec/issues/1832), [#1841](https://github.com/matrix-org/matrix-spec/issues/1841), [#1852](https://github.com/matrix-org/matrix-spec/issues/1852), [#1853](https://github.com/matrix-org/matrix-spec/issues/1853))
- Specify the encoding to be used when generating QR codes for device verification. ([#1839](https://github.com/matrix-org/matrix-spec/issues/1839))
- Clarify that an access token is optional on the `POST /account/password` and `POST /account/deactivate` endpoints. ([#1843](https://github.com/matrix-org/matrix-spec/issues/1843))
- Use RFC 2119 keywords more consistently. ([#1846](https://github.com/matrix-org/matrix-spec/issues/1846), [#1861](https://github.com/matrix-org/matrix-spec/issues/1861))
- Move size limits for user, room and event IDs into the appendix and clarify that the length is to be measured in bytes. ([#1850](https://github.com/matrix-org/matrix-spec/issues/1850))
- Clarify that relations recursion should be capped at a certain depth. ([#1854](https://github.com/matrix-org/matrix-spec/issues/1854))
- Add missing secrets, third-party invites and room tagging modules to feature profiles table. ([#1860](https://github.com/matrix-org/matrix-spec/issues/1860))
- Clarify when server name is used and link to the definition. ([#1862](https://github.com/matrix-org/matrix-spec/issues/1862))
- Clarify where keys reside when checking an `m.room.encrypted` event. ([#1863](https://github.com/matrix-org/matrix-spec/issues/1863))
- Clarify that `/media/v3/upload/{serverName}/{mediaId}` requires authentication. ([#1872](https://github.com/matrix-org/matrix-spec/issues/1872))
- Use of the Client-Server API `/_matrix/media/*` endpoints is now deprecated. New, authenticated, endpoints are available instead. ([#1858](https://github.com/matrix-org/matrix-spec/issues/1858))
- Media downloads and thumbnails are now authenticated, as per [MSC3916](https://github.com/matrix-org/matrix-spec-proposals/pull/3916). ([#1858](https://github.com/matrix-org/matrix-spec/issues/1858), [#1869](https://github.com/matrix-org/matrix-spec/issues/1869))
**Spec Clarifications**
- Link to existing grammar where possible in types. ([#1813](https://github.com/matrix-org/matrix-spec/issues/1813))
- Clarify that whitespace around commas is allowed in the `X-Matrix``Authorization` header value params list. ([#1818](https://github.com/matrix-org/matrix-spec/issues/1818))
- Clarify that the `event` field of the `/v2/send_join` response is only required when the event is signed by the resident server. ([#1834](https://github.com/matrix-org/matrix-spec/issues/1834), [#1840](https://github.com/matrix-org/matrix-spec/issues/1840))
- Replace references to RFC 7235 and RFC 7230 that are obsoleted by RFC 9110. ([#1844](https://github.com/matrix-org/matrix-spec/issues/1844))
- Fix various typos throughout the specification. ([#1877](https://github.com/matrix-org/matrix-spec/issues/1877))
- Clarify that appservices should be notified of events relating to the `sender_localpart` user. ([#1810](https://github.com/matrix-org/matrix-spec/issues/1810))
- Authentication using a query string is now deprecated, as per [MSC4126](https://github.com/matrix-org/matrix-spec-proposals/issues/4126). The `Authorization` header should be used instead. ([#1808](https://github.com/matrix-org/matrix-spec/issues/1808))
- Clarify that redaction events are still subject to all applicable auth rules. ([#1824](https://github.com/matrix-org/matrix-spec/issues/1824))
- Fix various typos throughout the specification. ([#1827](https://github.com/matrix-org/matrix-spec/issues/1827), [#1848](https://github.com/matrix-org/matrix-spec/issues/1848))
- Fix the rendering of the event format for room versions 1 and 2. ([#1883](https://github.com/matrix-org/matrix-spec/issues/1883))
- Generate the Table of Contents with Hugo rather than JavaScript. ([#1884](https://github.com/matrix-org/matrix-spec/issues/1884))
- Deprecate linking to events in rooms identified by alias, as per [MSC4132](https://github.com/matrix-org/matrix-spec-proposals/pull/4132). ([#1823](https://github.com/matrix-org/matrix-spec/issues/1823))
- Define common cryptographic key representation. ([#1819](https://github.com/matrix-org/matrix-spec/issues/1819))
- Move size limits for user, room and event IDs into the appendix and clarify that the length is to be measured in bytes. ([#1850](https://github.com/matrix-org/matrix-spec/issues/1850))
- Update the spec release process and related documentation. ([#1759](https://github.com/matrix-org/matrix-spec/issues/1759))
- Fix npm release script for `@matrix-org/spec`. ([#1765](https://github.com/matrix-org/matrix-spec/issues/1765))
- Formatting fixes in `CONTRIBUTING.rst`. ([#1769](https://github.com/matrix-org/matrix-spec/issues/1769))
- Improve rendering on mobile devices. ([#1770](https://github.com/matrix-org/matrix-spec/issues/1770), [#1771](https://github.com/matrix-org/matrix-spec/issues/1771))
- Fix the OpenAPI definition of the security schemes. ([#1772](https://github.com/matrix-org/matrix-spec/issues/1772))
- Simplify uses of `resolve-refs` partial. ([#1773](https://github.com/matrix-org/matrix-spec/issues/1773))
- Fix Hugo warnings. ([#1775](https://github.com/matrix-org/matrix-spec/issues/1775), [#1788](https://github.com/matrix-org/matrix-spec/issues/1788))
- Solve `allOf` recursively in OpenAPI and JSON Schemas. ([#1787](https://github.com/matrix-org/matrix-spec/issues/1787))
- Fix property type resolution in `render-object-table` partial. ([#1789](https://github.com/matrix-org/matrix-spec/issues/1789))
- Factor out common definition of `Tag` type. ([#1793](https://github.com/matrix-org/matrix-spec/issues/1793))
- Update the version of Hugo used to render the spec to v0.124.1. ([#1794](https://github.com/matrix-org/matrix-spec/issues/1794))
- Add support for pattern formats for `patternProperties`. ([#1796](https://github.com/matrix-org/matrix-spec/issues/1796))
- Clean up unnecessary `allOf`s in OpenAPI definitions. ([#1797](https://github.com/matrix-org/matrix-spec/issues/1797))
- Show information about "Additional Properties" in object tables. ([#1798](https://github.com/matrix-org/matrix-spec/issues/1798))
- Fix anchors for schemas under `oneOf`. ([#1799](https://github.com/matrix-org/matrix-spec/issues/1799))
- Use reference to `OneTimeKeys` schema in OpenAPI definitions. ([#1800](https://github.com/matrix-org/matrix-spec/issues/1800))
- Do not use the `title` of objects containing only `additionalProperties` or `patternProperties`. ([#1801](https://github.com/matrix-org/matrix-spec/issues/1801))
- Add anchors in `definition` shortcode. ([#1802](https://github.com/matrix-org/matrix-spec/issues/1802))
- Set python version for the Towncrier CI job. ([#1805](https://github.com/matrix-org/matrix-spec/issues/1805))
- Replace `set-output` with environment files in CI. ([#1806](https://github.com/matrix-org/matrix-spec/issues/1806))
- Use `patternProperties` in more places with supported formats. ([#1813](https://github.com/matrix-org/matrix-spec/issues/1813))
- Add support for rendering string formats. ([#1814](https://github.com/matrix-org/matrix-spec/issues/1814))
- Refactor the OpenAPI definitions of the content repository endpoints. ([#1822](https://github.com/matrix-org/matrix-spec/issues/1822))
- Clean up pull request template. ([#1831](https://github.com/matrix-org/matrix-spec/issues/1831))
- Do not add empty arrays to examples. ([#1849](https://github.com/matrix-org/matrix-spec/issues/1849))
- Generate the Table of Contents with Hugo rather than JavaScript. ([#1851](https://github.com/matrix-org/matrix-spec/issues/1851), [#1885](https://github.com/matrix-org/matrix-spec/issues/1885))
- Fix syntax errors in the spec release issue template. ([#1856](https://github.com/matrix-org/matrix-spec/issues/1856))
- Use environment variables for Netlify build job. ([#1865](https://github.com/matrix-org/matrix-spec/issues/1865))
- Render added/changed in info on request and response content types. ([#1876](https://github.com/matrix-org/matrix-spec/issues/1876))
- Fix validation errors in generated HTML. ([#1880](https://github.com/matrix-org/matrix-spec/issues/1880))
- Ensure most generated HTML IDs are unique. ([#1881](https://github.com/matrix-org/matrix-spec/issues/1881))
- Allow to specify a prefix for generated HTML IDs of API endpoints. ([#1882](https://github.com/matrix-org/matrix-spec/issues/1882))