[Quoth]

Yes, insecure keyboard is more serious. Also due to flaws in USB / USB HID a maliciously made USB mouse can inject malware.

TBH I'd not worry about the wireless mouse security, except the same proprietary dongle is often also in a set* with a keyboard.

Close without a concealed dish in a van/truck with cloth / fibreglass sides/panels.

There is ONE documented case I know of miscreants renting the unit next door. That enables sniffing WiFi, BT and so called "powerline" ethernet which isn't blocked by anything at the fuse/meterbox. Ethernet over your maoins wiring may or may not be encrypted securely.

Sorry for going off topic on Reading Ranting!

EDIT
[* Actually someone gave me a new MS keyboard & mouse wireless set that used a proprietary dongle. I tried it with a PC that's on a TV, but gave I it away to someone. I have a small pocket sized keyboard with touchpand and dongle that mysteriously works to type text into TV. We don't have the TV on ethernet or WiFi. I last used it for a UK postcode on the tuning scanning.]