DOM XSS on 50x.html page

How it was found

Hello,

The is a DOM XSS vulnerability on https://duckduckgo.com/50x.html, it seems like the sink is DIV.innerHTML and the source is location.search. The PoC url is: https://duckduckgo.com/50x.html?e=&atb=test%22/%3E%3Cimg%20src=x%20onerror=alert(document.domain);%3E

The code that is causing this XSS is located in: https://duckduckgo.com/lib/l110.js Line 26, Column 60903

Below is the part of the vulnerable code: b5.createElement("div")); cg = (m.exec(b7) || ["", ""])[1].toLowerCase(); b4 = R[cg] || R._default; ce.innerHTML = b4[1] + b7.replace(aB, "<$1></$2>") + b4[2]; cb = b4[0]; while (cb--) { ce=ce.lastChild } if(!bI.support.leadingWhitespace&&b2.test(b7))

Screenshot: {F342240}

Impact

The attacker can execute JS code.