Ticket #26649: escaped-shortcodes-get-the-excerpt.patch

src/wp-includes/shortcodes.php

@@ -305 +305 @@
 function strip_shortcode_tag( $m ) {
         // allow [[foo]] syntax for escaping a tag
         if ( $m[1] == '[' && $m[6] == ']' ) {
-                return '[' . substr( $m[0], 2, -1 );
+                // return escaped opening bracket to prevent expansion during get_the_excerpt
+                return '[' . substr( $m[0], 2, -1 );
         }
         return $m[1] . $m[6];
 }