Ticket #50784: 50784.substr.diff

src/wp-admin/includes/file.php

@@ -2356 +2356 @@
         }
 
         // Verify that file to be invalidated has a PHP extension.
-        if ( ! preg_match( '/\.(?:php)$/i', $filepath ) ) {
+        if ( '.php' !== strtolower( substr( $filepath, -4 ) ) ) {
                 return false;
         }