In Bug 33711, Krinkle said it is the way to go that we have to add dependencies for mw.util. But mediawiki.legacy.wikibits uses this module and does not wait and fails in non-debug-mode only. The following line was extracted by firebug:

'windows')!=-1;window.is_ff2_x11=is_ff2&&clientPC.indexOf('x11')!=-1;window.is_opera=window.is_opera_preseven=window.is_opera_95=window.opera6_bugs=window.opera7_bugs=window.opera95_bugs=false;if(clientPC.indexOf('opera')!=-1){window.is_opera=true;window.is_opera_preseven=window.opera&&!document.childNodes;window.is_opera_seven=window.opera&&document.childNodes;window.is_opera_95=/opera\/(9\.[5-9]|[1-9][0-9])/.test(clientPC);window.opera6_bugs=is_opera_preseven;window.opera7_bugs=is_opera_seven&&!is_opera_95;window.opera95_bugs=/opera\/(9\.5)/.test(clientPC);}window.ie6_bugs=false;if(/msie ([0-9]{1,}[\.0-9]{0,})/.exec(clientPC)!=null&&parseFloat(RegExp.$1)<=6.0){ie6_bugs=true;}window.doneOnloadHook=undefined;if(!window.onloadFuncts){window.onloadFuncts=[];}window.addOnloadHook=function(hookFunct){if(!doneOnloadHook){onloadFuncts[onloadFuncts.length]=hookFunct;}else{hookFunct();}};window.importScript=function(page){var uri=mw.config.get('wgScript')+'?title='+mw.util.wikiUrlencode(page)+

Note the mw.util.wikiUrlencode.

Version: 1.20.x
Severity: normal