Don Jenkins wrote:
My garage door opens by itself from time to time. The make is called
"Challenger", and it is distributed by Swift Garage Door Systems.

Can anyone suggest a cure?

Your opener code is shared with a neighbor's opener. Change the code.
Usually the code changes automatically to inhibit the use of scanners,
but you might have to change it manually. Check the manual or the
manufacturer's web site for instructions.

R