New members getting password changed email on first login

Hello,

I am a developer for a company that has a system runing on EE V5 which signs up a lot of new members frequently.

Recently new member registrations are receiving an email telling them the password has changed on their first login. There is also a strange url in the body as can be seen in my screen grab attached.

Does anybody know what might cause this and how to stop the system telling people password was changed when it is their first login?

Thank you in advance

Andrew