Unknown iOS Safari saved Password won't delete.

This is related to Safari on iOS, not OSX.

I've just noticed on my phone under settings / safari / saved passwords, that I have an entry saved, which I didn't put there and I don't recognise the user name and or password.

It's a numerical email address and also the password is 6 digits, due to this I'm thinking that it possibly been installed by an app on my phone? The website field appears to be blank. The really strange part is that whenever I try to delete the saved password, it keeps coming back. If I change the password value, it automatically creates a new password entry with the same user name and the original password.

I've checked another phone and they don't have any passwords saved in their settings, so it's not a legit OS password.

Here is the user name, it's for a domain that I've never visited before in my life.

Username: 77D7CD1A@7107.com

Pwd: 6 digits

Website: blank.

The behaviour seems a little suss to me. Does anyone have any ideas what it might be, or have you come across password which you can't seem to delete?

Cheers.