Qwik is a performance focused javascript framework. A potential mutation XSS vulnerability exists in Qwik for versions up to but not including 1.6.0. Qwik improperly escapes HTML on server-side rendering. It converts strings according to the rules found in the `render-ssr.ts` file. It sometimes causes the situation that the final DOM tree rendered on browsers is different from what Qwik expects on server-side rendering. This may be leveraged to perform XSS attacks, and a type of the XSS is known as mXSS (mutation XSS). This has been resolved in qwik version 1.6.0 and @builder.io/qwik version 1.7.3. All users are advised to upgrade. There are no known workarounds for this vulnerability.