Summary

One player could register multiple times.

Vulnerability Details

The method ThePredicter::register is responsible for registering users. It should revert when attempting to register user that already has registered but it does not handle all cases.
It's possible to have a duplicate if organizer approves the registration of a user that was already approved.

Impact

• Unexpected behaviour of the user's registration

• Filling array so less than 30 unique people can participate in the competition

Tools Used

Manual review

Recommendations

Rewrite the logic for ThePredicter::register in a way that checks if the user is already registered instead of relying on the statuses.
There are 2 variants about it:

1. Loop through the array ThePredicter::players to check if the player already exists

2. Make a storage variable with mapping type which stores registered user and check if user exists using it's as key instead of looping through array.