I was in a tipping comp years ago. At this workplace I had already warned the management against insecure email protocols but they wouldnt listen.
Anyway, came time for the company footy tipping comp.
Once I worked out which manager was running it, I used their plaintext password against their admin login to the tipping website. Worked straight up.
Every week I would make my tips, then after the games had been run but before Monday rolled around, I would use the admin access to change my tips.
Didnt try and hide it just went 100% victory every week.
The admin of the comp would even go out of his way to try and satisfy the very angry football fans that it wasnt run on company systems so theres no way that I could find my way in to change things.
In the end I fessed up, I couldnt get them to change the email system, but he apparently proactively took the password post it note off of his monitor which was nice.