The guessable credentials can find in most of the application. It may add for the testing purpose or an initial setup and later forget about it and added to the production server. Usage of common usernames and password leads to a successful brute-force attack. The most common used username and password combos gave below.
Even if it have brute-force prevention mechanism, most of the attackers first check manually with above credentials or use the framework default username and password.
Chances of a high success rate in the brute-force attack
Beagle recommends the following fixes:-