FirstBlood-#793Invalidate previously registered users by using duplicate invitations
This issue was discovered on FirstBlood v2

On 2021-10-28, axe Level 4 reported:


  1. Use test invitation code to register test users.

  2. Register test user again using test invitation code. Found that registration failed.

  3. Try another idea. To make it easier to distinguish, I'll register and test with other usernames.

  4. Register Sam users with test invitation code

    1. Register successfully

    2. Try logging in

    3. Login successful

  5. After testing Sam user can log in repeatedly !!! Until I registered Axe user with test invitation code -> found that Sam user strangely can't login anymore.

    1. Try to log in to Sam user -> Show: There was an error logging in.

    2. Try to log in to Axe user -> The login was found to be successful.

    3. Tried again to log in to the Sam user and found that the login failed!!! The user is no longer available.


  1. Description test invitation code can be registered repeatedly, but not expire!

  2. Explain that after the latest use of the invitation code, the previous registered account will be invalid

P3 Medium

Endpoint: /register.php

Parameter: inviteCode

Payload: NA

FirstBlood ID: 24
Vulnerability Type: Auth issues

The old invite code was deleted but when testing FirstBlood v2 the developers accidentally left the test code working.