On the adminCP login screen: if you enter an email address which isn't registered on the site you get the following notification:

Would recommend changing to an unmodified language pack as I am not able to reproduce this on an unmodified one. 

Thanks Jim.  I disabled every language pack except for the default, but when I tried logging back in to the adminCP with a bogus email I got a different error message entirely: "The email address or password was incorrect. Please try again (make sure your caps lock is off)."  So it seems like a different type of error altogether being flagged.

Moreover, it seems to be hard-coded; I can't find the language for my original error anywhere using the translation option, whereas the error I get with the default pack could be any of the following keys:

1. login_bad_username_or_password
2.  login_err_bad_password
3.  login_err_no_account

But all of these keys have the same values in my customised language pack (i.e. I didn't change them at all).  Thoughts?

54 minutes ago, LiquidFractal said:

But all of these keys have the same values in my customised language pack (i.e. I didn't change them at all).  Thoughts?

That's correct, we have changed this for security reasons, I'm just not sure why we have kept the condition and the 3 langstrings instead of returning only one generic error message in all cases:D