GHSA-2rwj-7xq8-4gx4: Qwik has a potential mXSS vulnerability due to improper HTML escaping

Summary

A potential mXSS vulnerability exists in Qwik for versions up to 1.6.0.

Details

Qwik improperly escapes HTML on server-side rendering. It converts strings according to the following rules:

https://github.com/QwikDev/qwik/blob/v1.5.5/packages/qwik/src/core/render/ssr/render-ssr.ts#L1182-L1208

• If the string is an attribute value:
  • " -> "
  • & -> &
  • Other characters -> No conversion
• Otherwise:
  • < -> <

  • -> > * & -> & * Other characters -> No conversion

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).

PoC

A vulnerable component:

import { component$ } from "@builder.io/qwik"; import { useLocation } from "@builder.io/qwik-city";

export default component$(() => {

// user input const { url } = useLocation(); const href = url.searchParams.get(“href”) ?? "https://example.com";

return ( <div> <noscript> <a href={href}>test</a> </noscript> </div> ); });

If a user accesses the following URL,

http://localhost:4173/?href=</noscript><script>alert(123)</script>

then, alert(123) will be executed.

Impact

XSS

References

• GHSA-2rwj-7xq8-4gx4
• QwikDev/qwik@7e742eb
• https://github.com/QwikDev/qwik/blob/v1.5.5/packages/qwik/src/core/render/ssr/render-ssr.ts#L1182-L1208
• https://nvd.nist.gov/vuln/detail/CVE-2024-41677