Accidental prepopulated contact form in Joomla

[Quatermass]

Really odd error here : The contact form on our Joomla website sometimes has prepopulated fields! For example, I just tested it, then my colleague logged in elsewhere to test it and found it prepopulated with my message! Cached somehow somewhere, I guess, but how and where?

[unixman_again]

What plugin are you using for this form?

[Quatermass]

Just the normal default Contacts Manager