* XML-RPC: Improve error messages for unprivileged users.
* External Libraries: Disable deserialization in Requests_Utility_FilteredIterator
* Embeds: Disable embeds on deactivated Multisite sites.
* Coding standards: Modify escaping functions to avoid potential false positives.
* XML-RPC: Return error message if attachment ID is incorrect.
* Upgrade/install: Improve logic check when determining installation status.
* Meta: Sanitize meta key before checking protection status.
* Themes: Ensure that only privileged users can set a background image when a theme is using the deprecated custom background page.
Brings the changes from [49380,49382-49388] to the 5.0 branch.
Props xknown, zieladam, peterwilsoncc, whyisjake, desrosj, dd32.
Built from https://develop.svn.wordpress.org/branches/5.0@49396
git-svn-id: http://core.svn.wordpress.org/branches/5.0@49155 1a063a9b-81f0-0310-95a4-ce76da25c4cd
* This moves our "development" versions from .dev.js to .js (same for css).
* The compressed version then moves from .js to .min.js (same for css).
By switching to the standard .min convention, it sets expectations for developers,
and works nicely with existing tools such as ack.
fixes#21633.
git-svn-id: http://core.svn.wordpress.org/trunk@21592 1a063a9b-81f0-0310-95a4-ce76da25c4cd
