@ Wolfgang. It is a new wireless Logitech mouse. It tunes out that it has this tiny little button to go back a page, and that button easily gets stuck. Right now it has been functioning for the last two minutes. Have to be quick writing this...

I hope my dad kept the receipt!
I thought so...

I had a similar problem with a Logitech mouse (just with another button). In case you will experience any trouble when trying to exchange the mouse at the seller's, you should contact Logitech CS. They are exceptionally helpful and courteous. I had lost the receipt, and yet got a replacement within 3 days.
Best wishes,
Wolfgang.