auth0-lock vulnerable to XSS via unsanitized placeholder property

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

• CVE-2019-20174: 0.72% estimated exploitation activity in the next 30 days; percentile 54.10 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Overview Auth0 Lock version 11.20.4 and earlier did not properly sanitize the generated HTML code. Customers using the additionalSignUpFields customization option to add a checkbox to the sign-up dialog that are passing a placeholder property obtained from an untrusted source (e.g. a query parameter) could allow cross-site scripting (XSS) on their signup pages. Am I affected? You are affected by this vulnerability if all of the following conditions apply: - You are using Auth0 Lock version 11.20.4 or earlier. - You pass additionalSignUpFields as options when initializing Lock which includes a field of type checkbox whose placeholder value is obtained from an untrusted source. An example of a vulnerable snippet is the following where the placeholder value is partially user-controlled by the name query parameter: How to fix that? Developers using Auth0’s signin solution Lock need to upgrade to version 11.21.0 or later. Version 11.21.0 introduces two changes: 1. The existing placeholder…

Published by the source

31 Jan 2020, 17:59 UTC

Last modified by the source

8 Nov 2023, 04:01 UTC

Source last checked

26 Oct 2026, 12:26 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-w2pf-g6r8-pg22

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-w2pf-g6r8-pg22

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# Patch Next advisory brief: CVE-2019-20174

Advisory: auth0-lock vulnerable to XSS via unsanitized placeholder property
IDs: CVE-2019-20174, GHSA-w2pf-g6r8-pg22
Record: https://patchnext.com/advisories/cve-2019-20174 (revision 2, source checked 26 Oct 2026, 12:26 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: auth0-lock 11.21.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm auth0-lock: affected < 11.21.0; fixed in 11.21.0

## Suggested inspection (read-only)
- `npm ls auth0-lock --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on auth0-lock.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-w2pf-g6r8-pg22 (OSV record GHSA-w2pf-g6r8-pg22 lists affected ranges: npm auth0-lock >=0 <11.21.0 (fixed))
- Verified: https://github.com/advisories/GHSA-w2pf-g6r8-pg22 (GitHub-reviewed advisory GHSA-w2pf-g6r8-pg22 lists affected ranges: npm auth0-lock >=0 <11.21.0)

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