Beta is not for weak people. Here in the MacMagazineWe have always made it very clear that trial versions of operating systems should not be installed on major devices as serious problems can happen (be it something linked to instability or even vulnerability). And that's exactly what happened to the iOS 13.
If you are using the third developer beta (or second public) of iOS 13, be aware that there is a very easy way to get access to usernames and passwords stored in Settings Passwords and Accounts Sites and Apps Passwords even with Touch / Face ID protection. All you have to do is tap on ?Site and App Passwords? over and over and over again, one hour, even without authentication, as reported on Reddit and shared by the YouTube channel. iDeviceHelp:
Apple has already been informed of the problem, but has not yet released a new version of testing with the patch.
Of course, to have access to iPhone Settings, one must necessarily have the device in hand and it must have been unlocked with Touch / Face ID or password. Still, it is still a serious / important enough vulnerability for you, who are testing iOS 13, to know.
We'll see if everything is properly fixed in the fourth beta for developers (and the third for Apple Beta Software Program participants).