Ticket #39797: 39797.1.diff

src/wp-includes/js/customize-preview.js

@@ -145 +145 @@
                                 return;
                         }
 
+                        // Allow internal jump links and JS links to behave normally without preventing default.
                         isInternalJumpLink = ( '#' === link.attr( 'href' ).substr( 0, 1 ) );
-
-                        // Allow internal jump links to behave normally without preventing default.
-                        if ( isInternalJumpLink ) {
+                        if ( isInternalJumpLink || ! /^https?:$/.test( link.prop( 'protocol' ) ) ) {
                                 return;
                         }
 
@@ -334 +333 @@
                         return;
                 }
 
-                // Ignore links with href="#" or href="#id".
-                if ( '#' === $( element ).attr( 'href' ).substr( 0, 1 ) ) {
+                // Ignore links with href="#", href="#id", or non-HTTP protocols (e.g. javascript: and mailto:).
+                if ( '#' === $( element ).attr( 'href' ).substr( 0, 1 ) || ! /^https?:$/.test( element.protocol ) ) {
                         return;
                 }