Comments: Strip html tags from comment content before blacklist_keys comparison.

Use `wp_kses()` to clean comment_content for preg_match against the blacklist_keys. Also includes some initial unit tests for `wp_blacklist_check()`.
Previously, if a blacklisted key was used in comment_content split by an html tag the regex in `wp_blacklist_check()` would not find a match. Example: Where "springfield" was a blacklisted word, if the content of a comment included `spring<i>field</i>" `wp_blacklist_check()` would not return true.

Props cfinke.
Fixes #37208.
Built from https://develop.svn.wordpress.org/trunk@38047


git-svn-id: http://core.svn.wordpress.org/trunk@37988 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/comment.php

@@ -1055,6 +1055,10 @@ function wp_blacklist_check($author, $email, $url, $comment, $user_ip, $user_age
 	$mod_keys = trim( get_option('blacklist_keys') );
 	if ( '' == $mod_keys )
 		return false; // If moderation keys are empty
+
+	// Ensure HTML tags are not being used to bypass the blacklist.
+	$comment_without_html = wp_kses( $comment, array() );
+
 	$words = explode("\n", $mod_keys );
 
 	foreach ( (array) $words as $word ) {
@@ -1072,7 +1076,7 @@ function wp_blacklist_check($author, $email, $url, $comment, $user_ip, $user_age
 			   preg_match($pattern, $author)
 			|| preg_match($pattern, $email)
 			|| preg_match($pattern, $url)
-			|| preg_match($pattern, $comment)
+			|| preg_match($pattern, $comment_without_html)
 			|| preg_match($pattern, $user_ip)
 			|| preg_match($pattern, $user_agent)
 		 )

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.6-beta2-38046';
+$wp_version = '4.6-beta2-38047';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.