title: Reflected XSS from the callback handler's error query parameter
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.
problem types: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
affected:
{
product: nextjs-auth0
vendor: auth0
versions:
status: affected, version: < 1.4.2
}
metrics:
cvssV3_1: [
attackComplexity: HIGH
attackVector: NETWORK
availabilityImpact: NONE
baseScore: 8
baseSeverity: HIGH
confidentialityImpact: HIGH
integrityImpact: HIGH
privilegesRequired: NONE
scope: CHANGED
userInteraction: REQUIRED
vectorString: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N
version: 3.1
]