Autocomplete shows wrong name

Question

i like the autocomplete feature; however, today it suggested my name in a form, but with "null" added, ie Joe null Bloggs. i'm sure i have never typed this in, so where did it come from? i'm suspicious that someone else has somehow typed it (though i'm the only person who has access to my computer)
== This happened ==
Just once or twice
== today

Answer 1

In my case, I have a field admin_phone_extension that is getting filled in with the saved "email" field on a specific page.
I can verify this by logging in to our application with the form history control open, see the "email" field saved, delete that email field only, then navigate to the page in question, the admin_phone_extension is blank.
Log out then log in and navigate to that page without messign with the saved history, adn the admin_phone_extension field is filled in with the email.
the markup for the field is:
<input name="admin_phone_extension" value="<?=(isset($advertiser['admin_phone_extension'])?$advertiser['admin_phone_extension']:'')?>" style="width:35px;" type="text" />
so why it is getting autofilled with the saved contents of the "email" field is beyond me.
One of my coworkers has a problem on a gaming site where every time she logs in and goes to edit her account on http://taint.rtgc.org, it fills in a field named "phone" with the value from a field named "login"
And this happens EVERY TIME she goes to that site.
We can possibly provide more information in private emails, as both of these issues happen behind a login which we cannot publish publicly.