pop up ads in WordPress?

I’m not sure if this is the right forum. Hope so.

I recently upgraded to WP 4.0. Now I am getting pop up ads every time I go from one page to another [as admin]. They do not appear in the web site, only when I am in WP-admin.
Is this a virus, or mutant plugin, or ????

This is driving me nuts! They are constant.

Any help – thank you.