diff --git a/core/js/js.js b/core/js/js.js
index e8c51a37b60..ba8e1597023 100644
--- a/core/js/js.js
+++ b/core/js/js.js
@@ -2666,10 +2666,19 @@ $.fn.position = function( options ) {
 
 	var atOffset, targetWidth, targetHeight, targetOffset, basePosition, dimensions,
 
-		// Make sure string options are treated as CSS selectors
-		target = typeof options.of === "string" ?
-			$( document ).find( options.of ) :
-			$( options.of ),
+		// Make sure string options are treated as CSS selectors and avoid HTML parsing
+		target = ( function( of ) {
+			if ( typeof of === "string" ) {
+				return $( document ).find( of );
+			}
+			if ( of && of.target ) {
+				return $( of.target );
+			}
+			if ( of && ( of.jquery || of.nodeType || of === window || of === document ) ) {
+				return $( of );
+			}
+			return $();
+		} )( options.of ),
 
 		within = $.position.getWithinInfo( options.within ),
 		scrollInfo = $.position.getScrollInfo( within ),