Hey, so I leave my computer on overnight because I have issues with shutting it down (it's old and clunky

) and this morning when I got up and checked it there was a pop-up window waiting for me on my desktop, asking for user verification for the site '
www.susans.org' and said something about 'for site staff'. It was just one short line and then a box for me to put my username and password.
I was still loged on to the site, and I'm always really cautious about giving info away, so I pressed cancel and it disappeared, and I haven't has any issues accessing the forum since. Is this normal, or was something else trying to get logon information from me?