+* Added several JavaScript libraries for uploading files to MediaWiki
+ from the client-side. See documentation for mw.Upload and its
+ subclasses for more information.
+* Added OOUI dialogs and layout for file upload interfaces. See
+ documentation for mw.Upload.Dialog, mw.Upload.BookletLayout and its
+ subclasses for more information.
+
+== extension.json changes in 1.26 ==
+* (T99344) The extension.json schema is now versioned. All extensions
+ and skins should set a "manifest_version" property corresponding to
+ the schema version they were written for. The only supported version
+ currently is "1".
+* (T102523) The error message if a non-array attribute is set was improved.
+* (T107646) Configuration settings can now specify how they should be merged,
+ which is necessary for arrays using integer keys.
+* (T110389) Adding namespaces through extension.json now actually works
+* $wgNamespaceProtection can now be set in extension.json.
+* $wgCapitalLinkOverrides can now be set in extension.json.
+* (T97186) Extensions using a custom prefix for their configuration settings
+ can now set a "_prefix" key to override the default of "wg".
+* (T99084) Extensions can now specify what MediaWiki core versions they
+ depend upon.
+* (T105236) The extension.json schema now validates custom classes in
+ the "ResourceModules" property properly.
+
+=== External library changes in 1.26 ===
+==== Upgraded external libraries ====