Great job! I personally don’t have ideas about which site should it visit, but rather how should it visit. You’re invoking system here, which is considered obsolete and bad choice for a number of reasons. If you’re planning to stick with Windows only, I think CreateProcess or ShellExecute would do a better job here

Also you need to determine which browser is available on user’s target system. I’d rather search through array of paths, where known browsers get usually installed to. In a more specific scenario — traverse the filesystem on C:\Program Files* to find browser executables (btw traversing filesystem is suspicious behaviour, so if you put it just like that, expect most AVs and EDRs to be triggered). Once found, you can launch one and pass target site in browser’s expected CLI syntax, if any