Fix for URL sanitization in `wp_kses_bad_protocol_once()`.

Merges [45997] to the 5.1 branch.

Props irsdl, sstoqnov, whyisjake.
Built from https://develop.svn.wordpress.org/branches/5.1@46002


git-svn-id: http://core.svn.wordpress.org/branches/5.1@45813 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/kses.php

@@ -1657,6 +1657,7 @@ function wp_kses_html_error( $string ) {
  * @return string Sanitized content.
  */
 function wp_kses_bad_protocol_once( $string, $allowed_protocols, $count = 1 ) {
+	$string  = preg_replace( '/(&#0*58(?![;0-9])|&#x0*3a(?![;a-f0-9]))/i', '$1;', $string );
 	$string2 = preg_split( '/:|&#0*58;|&#x0*3a;/i', $string, 2 );
 	if ( isset( $string2[1] ) && ! preg_match( '%/\?%', $string2[0] ) ) {
 		$string   = trim( $string2[1] );