fix: Parse Server OAuth2 authentication adapter account takeover via identity spoofing ([GHSA-fr88-w35c-r596](https://github.com/parse-community/parse-server/security/advisories/GHSA-fr88-w35c-r596)) (#10145)

spec/Adapters/Auth/oauth2.spec.js

@@ -128,6 +128,62 @@ describe('OAuth2Adapter', () => {
         adapter.validateAuthData(authData, null, validOptions)
       ).toBeRejectedWithError('OAuth2 access token is invalid for this user.');
     });
+
+    it('should default useridField to sub and reject mismatched user ID', async () => {
+      const adapterNoUseridField = new OAuth2Adapter.constructor();
+      adapterNoUseridField.validateOptions({
+        tokenIntrospectionEndpointUrl: 'https://provider.example.com/introspect',
+      });
+
+      const authData = { id: 'victim-user-id', access_token: 'attackerToken' };
+      const mockResponse = {
+        active: true,
+        sub: 'attacker-user-id',
+      };
+
+      mockFetch([
+        {
+          url: 'https://provider.example.com/introspect',
+          method: 'POST',
+          response: {
+            ok: true,
+            json: () => Promise.resolve(mockResponse),
+          },
+        },
+      ]);
+
+      await expectAsync(
+        adapterNoUseridField.validateAuthData(authData, null, {})
+      ).toBeRejectedWithError('OAuth2 access token is invalid for this user.');
+    });
+
+    it('should default useridField to sub and accept matching user ID', async () => {
+      const adapterNoUseridField = new OAuth2Adapter.constructor();
+      adapterNoUseridField.validateOptions({
+        tokenIntrospectionEndpointUrl: 'https://provider.example.com/introspect',
+      });
+
+      const authData = { id: 'user-id', access_token: 'validAccessToken' };
+      const mockResponse = {
+        active: true,
+        sub: 'user-id',
+      };
+
+      mockFetch([
+        {
+          url: 'https://provider.example.com/introspect',
+          method: 'POST',
+          response: {
+            ok: true,
+            json: () => Promise.resolve(mockResponse),
+          },
+        },
+      ]);
+
+      await expectAsync(
+        adapterNoUseridField.validateAuthData(authData, null, {})
+      ).toBeResolvedTo({});
+    });
   });
 
   describe('requestTokenInfo', () => {
@@ -281,6 +337,57 @@ describe('OAuth2Adapter', () => {
       );
     });
 
+    it('should reject account takeover when useridField is omitted and attacker uses their own token with victim ID', async () => {
+      await reconfigureServer({
+        auth: {
+          mockOauth: {
+            tokenIntrospectionEndpointUrl: 'https://provider.example.com/introspect',
+            authorizationHeader: 'Bearer validAuthToken',
+            oauth2: true,
+          },
+        },
+      });
+
+      // Victim signs up with their own valid token
+      mockFetch([
+        {
+          url: 'https://provider.example.com/introspect',
+          method: 'POST',
+          response: {
+            ok: true,
+            json: () => Promise.resolve({
+              active: true,
+              sub: 'victim-sub-id',
+            }),
+          },
+        },
+      ]);
+
+      const victimAuthData = { access_token: 'victimToken', id: 'victim-sub-id' };
+      const victim = await Parse.User.logInWith('mockOauth', { authData: victimAuthData });
+      expect(victim.id).toBeDefined();
+
+      // Attacker tries to log in with their own valid token but claims victim's ID
+      mockFetch([
+        {
+          url: 'https://provider.example.com/introspect',
+          method: 'POST',
+          response: {
+            ok: true,
+            json: () => Promise.resolve({
+              active: true,
+              sub: 'attacker-sub-id',
+            }),
+          },
+        },
+      ]);
+
+      const attackerAuthData = { access_token: 'attackerToken', id: 'victim-sub-id' };
+      await expectAsync(Parse.User.logInWith('mockOauth', { authData: attackerAuthData })).toBeRejectedWith(
+        new Parse.Error(Parse.Error.OBJECT_NOT_FOUND, 'OAuth2 access token is invalid for this user.')
+      );
+    });
+
     it('should handle error when token introspection endpoint is missing', async () => {
       await reconfigureServer({
         auth: {

src/Adapters/Auth/oauth2.js

@@ -5,7 +5,7 @@
  * @param {Object} options - The adapter configuration options.
  * @param {string} options.tokenIntrospectionEndpointUrl - The URL of the token introspection endpoint. Required.
  * @param {boolean} options.oauth2 - Indicates that the request should be handled by the OAuth2 adapter. Required.
- * @param {string} [options.useridField] - The field in the introspection response that contains the user ID. Optional.
+ * @param {string} [options.useridField='sub'] - The field in the introspection response that contains the user ID. Defaults to `sub` per RFC 7662.
  * @param {string} [options.appidField] - The field in the introspection response that contains the app ID. Optional.
  * @param {string[]} [options.appIds] - List of allowed app IDs. Required if `appidField` is defined.
  * @param {string} [options.authorizationHeader] - The Authorization header value for the introspection request. Optional.
@@ -66,7 +66,7 @@ class OAuth2Adapter extends AuthAdapter {
     }
 
     this.tokenIntrospectionEndpointUrl = options.tokenIntrospectionEndpointUrl;
-    this.useridField = options.useridField;
+    this.useridField = options.useridField || 'sub';
     this.appidField = options.appidField;
     this.appIds = options.appIds;
     this.authorizationHeader = options.authorizationHeader;