I bought this Onn mouse several weeks ago and it worked perfectly on my laptop. I’m about to run my antivirus software because my mouse all of a sudden starts typing somehwhere else. For an example, my laptop does this thing (ever since about a month ago) where sometimes, while I’m typing, It swithes lines randomly. It’s annoying, but I’m used to it now. Anyways, now it opens up things while I type. This post right now is taking forever because it keeps highlighting the search bar for no reason. About every 2 - 5 chars.
Now, when I’m programming, it opens up the the type hierarchy. This is really annoying, especially since I type fast. What would be the matter?
Wired or wireless mouse? Are the batteries charged and it the receiver free of obstructions (wireless)? Is the sensor clean on the mouse? Have you tried switching USB ports (wired) or checked to see if there’s a conflict between the touchpad and mouse on the laptop? What happens if you disable the touchpad? It’d probably not a virus since the behaviour would make it obvious. Maybe try looking for a driver update if one is available.
No driver updates and it’s a wired mouse
Are you ever brushing up against the touch pad with your hand? This happens to me quite often when I don’t disable it.
I almost threw my notebook at the wall out of anger because of this. My touch pad is so sensitive that you almost can’t work with it enabled. Some touchpads allow to configure the touch sensitivity. This might help.
You know 15 years ago the mouse would have just been tossed in the bin because it’s obviously broken 
I use this method with HDDs and Mouses:
while (iStillHavePatience) {
hitItAgainstSomethingHard();
if (itWorks("!!!")) break;
}
works like 80% of the time.