Capabilities: Prevent users having the `do_not_allow` capability.

Meta capabilities use the capability `do_not_allow` to indicate a user should be blocked from performing a particular action. This ensures users can not have the capability as it would cause unexpected behaviour.

Props johnbillion.
Fixes #41059.


Built from https://develop.svn.wordpress.org/trunk@40993


git-svn-id: http://core.svn.wordpress.org/trunk@40843 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-user.php

@@ -748,6 +748,9 @@ class WP_User {
 		// Everyone is allowed to exist.
 		$capabilities['exist'] = true;
 
+		// Nobody is allowed to do things they are not allowed to do.
+		unset( $capabilities['do_not_allow'] );
+
 		// Must have ALL requested caps.
 		foreach ( (array) $caps as $cap ) {
 			if ( empty( $capabilities[ $cap ] ) )

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.9-alpha-40992';
+$wp_version = '4.9-alpha-40993';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.