After fruitlessly searching online for the default username and password for the APC's PowerChute Business Edition Agent (client for accessing and managing APC UPS units via Serial interface), and eventually re-installing the entire application to gain access to it, I decided to post my findings here to hopefully save some of you time seaching:
Q: What is the default username and password for the APC's PowerChute Business Edition Agent?
A: Unfortunately (for your purpose; from security perspective - it's a good thing) all the recent versions of the PowerChute Business Edition (at least starting with 8.0.1 Single Node agent, which is what I was using) do not provide a default username and password, but instead ask you to select them during installation (right after selecting the UPS type and COM port).
However, while there is no default username and password for the PowerChute Business Edition Agent 8.0.1, you can easily reset it by uninstalling and reinstalling the application (free version can be downloaded from the APC website here, commercial versions can be purchased here). I hope this helps.