How can I reset my Sonarr and Radarr login passwords?

I just installed Sonarr and Radarr on my seedbox and I logged in using the default credentials from my client area. After getting everything configured all seemed to be working as expected. Today, however, I'm not able to login to either of the apps and I never changed the passwords from the default. How can I change the passwords without reinstalling these apps?

Thanks.