* (bug 42184) $wgUploadSizeWarning missing second variable
* (bug 40326) Check if files exist with a different extension during uploading
* (bug 34798) Updated CSS for Atom/RSS recent changes feeds to match on-wiki diffs.
+* (bug 42430) Calling numRows on MySQL no longer propagates unrelated errors.
=== API changes in 1.21 ===
* prop=revisions can now report the contentmodel and contentformat.