We have recently become aware of a security vulnerability that allows for someone to gain access to your account temporarily. We urge you to connect only to servers that you trust in order to limit the cases where this occurs. We also wish to encourage you to only install client mods that you trust because those have a large possibility of being able to steal your account information. We are working on getting in contact with the Mojang team to resolve this issue as soon as possible.

Note to server admins: - Please refrain from logging into other servers that don't own with your primary account for the time being as to prevent people from having temporary admin access on your servers.

Edit: We being several members of the r/MCPublic servers

Edit: Logging out and back in has been found that it wont help. This can only occur when you connect to the server and as soon as they log off, they can no longer use your account.