Problems caused by Windows Update

While I have not had this problem in a month or so, I started the
computer this afternoon and find it is back.

I have a Toshiba Satelite with Windows 8.1 4gb ram i-3CPU. 500gb disk

This afternoon when I cam home and turned the computer on both
Thunderbird 31.5.0 and Firefox 36.0.1 would not come up with out the
warning they had to be reset. Without doing any thing to any thing, I
closed the warning windows.

Based on previous experience, I checked to see if there was a Windows
8.1 update. The Windows Malicioius Software remove tool wanted to be
updated.

WITHOUT DOING ANYTHING TO THE MOZILLA PRODUCTS, I down loaded the
Malicious Software Update, and allowed it to install. I rebooted the
computer. I then went on to do what I had turned the computer to do
with Mozilla Firefox and Thunderbird. Both open normally with out
changing any thing in the program.

This has been a common occurance for the past year. I don't know if the
Malicious Software Removal Tool was involved with every update but this
morning it was the only program updated.

As I said this has been going on for many months through several
revision of the Mozilla products.

Why does Windows think it necessary to interfer with other product, just
because they have an update to install?