The vulnerability is a Credential Leak by App Logic that leads to the unauthorized disclosure of the Cross-Site Request Forgery (XSRF) token to an attacker-controlled domain.

Angular's HttpClient has a built-in XSRF protection mechanism that works by checking if a request URL starts with a protocol (http:// or https://) to determine if it is cross-origin. If the URL starts with protocol-relative URL (//), it is incorrectly treated as a same-origin request, and the XSRF token is automatically added to the X-XSRF-TOKEN header.

Affected versions                  Patched versions
>=21.0.0-next.0 < 21.0.1           21.0.1
>=20.0.0-next.0 < 20.3.14         20.3.14
>=19.0.0-next.0 < 19.2.16        19.2.16
<= 18.2.14                                   none

Workarounds

Developers should avoid using protocol-relative URLs (URLs starting with //) in HttpClient requests. All backend communication URLs should be hardcoded as relative paths (starting with a single /) or fully qualified, trusted absolute URLs.

react-server-dom-webpack
react-server-dom-parcel
react-server-dom-turbopack