oauth2-server (aka node-oauth2-server) through 3.1.1 implements OAuth 2.0 without PKCE. It does not prevent authorization code injection. This is similar to CVE-2020-7692. NOTE: the vendor states 'As RFC7636 is an extension, I think the claim in the Readme of "RFC 6749 compliant" is valid and not misleading and I also therefore wouldn't describe this as a "vulnerability" with the library per se.

PKCE support is not implemented in accordance with the RFC for OAuth 2.0 for Native Apps. Without the use of PKCE, the authorization code returned by an authorization server is not enough to guarantee that the client that issued the initial authorization request is the one that will be authorized. An attacker is able to obtain the authorization code using a malicious app on the client-side and use it to gain authorization to the protected resource. This affects the package com.google.oauth-client:google-oauth-client before 1.31.0.