In one example of the present disclosure, a computing system is provided. The computing system is to initiate a power on self-test (POST) process, determine that a change has been made to system firmware configuration data, start a timer, and determine that the timer has expired. Thereafter, the computing system is to power-off and power-on the computing system, replace current system firmware configuration data with backup system firmware configuration data, and/or generate a notification indicating system firmware configuration data has been reverted.