diff --git a/spec/vulnerabilities.spec.js b/spec/vulnerabilities.spec.js
index 8645dd524c..a866689c24 100644
--- a/spec/vulnerabilities.spec.js
+++ b/spec/vulnerabilities.spec.js
@@ -4240,6 +4240,81 @@ describe('(GHSA-g4cf-xj29-wqqr) DoS via unindexed database query for unconfigure
   });
 });
 
+describe('(GHSA-2299-ghjr-6vjp) MFA recovery code reuse via concurrent requests', () => {
+  const mfaHeaders = {
+    'X-Parse-Application-Id': 'test',
+    'X-Parse-REST-API-Key': 'rest',
+    'Content-Type': 'application/json',
+  };
+
+  beforeEach(async () => {
+    await reconfigureServer({
+      auth: {
+        mfa: {
+          enabled: true,
+          options: ['TOTP'],
+          algorithm: 'SHA1',
+          digits: 6,
+          period: 30,
+        },
+      },
+    });
+  });
+
+  it('rejects concurrent logins using the same MFA recovery code', async () => {
+    const OTPAuth = require('otpauth');
+    const user = await Parse.User.signUp('mfauser', 'password123');
+    const secret = new OTPAuth.Secret();
+    const totp = new OTPAuth.TOTP({
+      algorithm: 'SHA1',
+      digits: 6,
+      period: 30,
+      secret,
+    });
+    const token = totp.generate();
+    await user.save(
+      { authData: { mfa: { secret: secret.base32, token } } },
+      { sessionToken: user.getSessionToken() }
+    );
+
+    // Get recovery codes from stored auth data
+    await user.fetch({ useMasterKey: true });
+    const recoveryCode = user.get('authData').mfa.recovery[0];
+    expect(recoveryCode).toBeDefined();
+
+    // Send concurrent login requests with the same recovery code
+    const loginWithRecovery = () =>
+      request({
+        method: 'POST',
+        url: 'http://localhost:8378/1/login',
+        headers: mfaHeaders,
+        body: JSON.stringify({
+          username: 'mfauser',
+          password: 'password123',
+          authData: {
+            mfa: {
+              token: recoveryCode,
+            },
+          },
+        }),
+      });
+
+    const results = await Promise.allSettled(Array(10).fill().map(() => loginWithRecovery()));
+
+    const succeeded = results.filter(r => r.status === 'fulfilled');
+    const failed = results.filter(r => r.status === 'rejected');
+
+    // Exactly one request should succeed; all others should fail
+    expect(succeeded.length).toBe(1);
+    expect(failed.length).toBe(9);
+
+    // Verify the recovery code has been consumed
+    await user.fetch({ useMasterKey: true });
+    const remainingRecovery = user.get('authData').mfa.recovery;
+    expect(remainingRecovery).not.toContain(recoveryCode);
+  });
+});
+
 describe('(GHSA-p2w6-rmh7-w8q3) SQL Injection via aggregate and distinct field names in PostgreSQL adapter', () => {
   const headers = {
     'Content-Type': 'application/json',
diff --git a/src/Adapters/Storage/Mongo/MongoTransform.js b/src/Adapters/Storage/Mongo/MongoTransform.js
index bbaefdd55a..0fd13017b3 100644
--- a/src/Adapters/Storage/Mongo/MongoTransform.js
+++ b/src/Adapters/Storage/Mongo/MongoTransform.js
@@ -304,11 +304,11 @@ function transformQueryKeyValue(className, key, value, schema, count = false) {
       return { key: 'times_used', value: value };
     default: {
       // Other auth data
-      const authDataMatch = key.match(/^authData\.([a-zA-Z0-9_]+)\.id$/);
+      const authDataMatch = key.match(/^authData\.([a-zA-Z0-9_]+)(\.(.+))?$/);
       if (authDataMatch && className === '_User') {
         const provider = authDataMatch[1];
-        // Special-case auth data.
-        return { key: `_auth_data_${provider}.id`, value };
+        const subField = authDataMatch[3];
+        return { key: `_auth_data_${provider}${subField ? `.${subField}` : ''}`, value };
       }
     }
   }
diff --git a/src/Adapters/Storage/Postgres/PostgresStorageAdapter.js b/src/Adapters/Storage/Postgres/PostgresStorageAdapter.js
index 7a2bafc460..7b7fc4ed97 100644
--- a/src/Adapters/Storage/Postgres/PostgresStorageAdapter.js
+++ b/src/Adapters/Storage/Postgres/PostgresStorageAdapter.js
@@ -340,6 +340,14 @@ const buildWhereClause = ({ schema, query, index, caseInsensitive }): WhereClaus
           patterns.push(`$${index}:raw = $${index + 1}::text`);
           values.push(name, fieldValue);
           index += 2;
+        } else if (
+          typeof fieldValue === 'object' &&
+          !Object.keys(fieldValue).some(key => key.startsWith('$'))
+        ) {
+          name = transformDotFieldToComponents(fieldName).join('->');
+          patterns.push(`($${index}:raw)::jsonb = $${index + 1}::jsonb`);
+          values.push(name, JSON.stringify(fieldValue));
+          index += 2;
         }
       }
     } else if (fieldValue === null || fieldValue === undefined) {
diff --git a/src/Routers/UsersRouter.js b/src/Routers/UsersRouter.js
index beaa08f6f2..9b63229df8 100644
--- a/src/Routers/UsersRouter.js
+++ b/src/Routers/UsersRouter.js
@@ -286,12 +286,35 @@ export class UsersRouter extends ClassesRouter {
 
     // If we have some new validated authData update directly
     if (validatedAuthData && Object.keys(validatedAuthData).length) {
-      await req.config.database.update(
-        '_User',
-        { objectId: user.objectId },
-        { authData: validatedAuthData },
-        {}
-      );
+      const query = { objectId: user.objectId };
+      // Optimistic locking: include the original array fields in the WHERE clause
+      // for providers whose data is being updated. This prevents concurrent requests
+      // from both succeeding when consuming single-use tokens (e.g. MFA recovery codes).
+      // Only array fields need locking — element removal is vulnerable to TOCTOU;
+      // scalar fields are simply overwritten and don't have concurrency issues.
+      if (user.authData) {
+        for (const provider of Object.keys(validatedAuthData)) {
+          const original = user.authData[provider];
+          if (original && typeof original === 'object') {
+            for (const [field, value] of Object.entries(original)) {
+              if (
+                Array.isArray(value) &&
+                JSON.stringify(value) !== JSON.stringify(validatedAuthData[provider]?.[field])
+              ) {
+                query[`authData.${provider}.${field}`] = value;
+              }
+            }
+          }
+        }
+      }
+      try {
+        await req.config.database.update('_User', query, { authData: validatedAuthData }, {});
+      } catch (error) {
+        if (error.code === Parse.Error.OBJECT_NOT_FOUND) {
+          throw new Parse.Error(Parse.Error.SCRIPT_FAILED, 'Invalid auth data');
+        }
+        throw error;
+      }
     }
 
     const { sessionData, createSession } = RestWrite.createSession(req.config, {