Index: branches/5.2.x/core/admin_templates/js/script.js
===================================================================
diff -u -N -r16276 -r16339
--- branches/5.2.x/core/admin_templates/js/script.js	(.../script.js)	(revision 16276)
+++ branches/5.2.x/core/admin_templates/js/script.js	(.../script.js)	(revision 16339)
@@ -365,7 +365,7 @@
 	set_hidden_field('events[trans]', 'OnLoad');
 
 	var $regex = new RegExp('(.*)\?env=(' + document.getElementById('sid').value + ')?-(.*?):(.*)');
-	var $t = $regex.exec(url)[3];
+	var $t = $regex.exec(rawurldecode(url))[3];
 
 	$kf.target = wnd;
 	submit_event(prefix, '', $t, url);
@@ -548,7 +548,7 @@
 function openSelector($prefix, $url, $dst_field, $window_size, $event) {
 	// get template name from url
 	var $regex = new RegExp('(.*)\?env=(' + document.getElementById('sid').value + ')?-(.*?):(m[^:]+)');
-	$regex = $regex.exec($url);
+	$regex = $regex.exec(rawurldecode($url));
 
 	var $t = $regex[3];
 
@@ -1852,7 +1852,7 @@
 		// setTimeout allows to call method indirectly. Without it whole idea won't work 2nd time (try adding 2 relations one after another)
 		setTimeout(
 			function () {
-				openSelector('adm', $ru.replace(/%5C/g, '\\') + '&merge_opener_stack=1');
+				openSelector('adm', $ru + '&merge_opener_stack=1');
 			},
 			200
 		);
@@ -1863,7 +1863,7 @@
 	window.focus();
 
 	if ( !(($force_skip_refresh === true) || (typeof $skip_refresh != 'undefined' && $skip_refresh)) ) {
-		window.location.href = $redirect_url.replace(/%5C/g, '\\');
+		window.location.href = rawurldecode($redirect_url);
 	}
 }
 
@@ -1874,6 +1874,20 @@
 	return document.getElementById($prepend + $mask.replace('#FIELD_NAME#', $field) + $append);
 }
 
+function rawurldecode(str) {
+
+	if ( str.indexOf('?') != -1 ) {
+		var $parts = str.split('?', 2);
+
+		return $parts[0] + ($parts.length == 2 ? '?' + rawurldecode($parts[1]) : '');
+	}
+
+	return decodeURIComponent((str + '').replace(/%(?![\da-f]{2})/gi, function () {
+		// PHP tolerates poorly formed escape sequences
+		return '%25';
+	}));
+}
+
 Array.prototype.each = function ($callback) {
 	var $result = null;