Reflected XSS from the callback handler's error query parameter

Vulnerability Description

The Auth0 Next.js SDK is a library for implementing user authentication in Next.js applications. Versions before and including `1.4.1` are vulnerable to reflected XSS. An attacker can execute arbitrary code by providing an XSS payload in the `error` query parameter which is then processed by the callback handler as an error message. You are affected by this vulnerability if you are using `@auth0/nextjs-auth0` version `1.4.1` or lower **unless** you are using custom error handling that does not return the error message in an HTML response. Upgrade to version `1.4.1` to resolve. The fix adds basic HTML escaping to the error message and it should not impact your users.

References

• https://github.com/auth0/nextjs-auth0/security/advisories/GHSA-954c-jjx6-cxv7
• https://github.com/auth0/nextjs-auth0/commit/6996e2528ceed98627caa28abafbc09e90163ccf
• https://www.npmjs.com/package/%40auth0/nextjs-auth0