Free of cost repair of software bug available at the Internet is called

A patch is a software update comprising code inserted (or patched) into the code of an executable program.
Typically, a patch is installed into an existing software program.
Patches are often temporary fixes between full releases of a software package.

Patches may do any of the following:
Fix a software bug
Install new drivers
Address new security vulnerabilities
Address software stability issues
Upgrade the software