If you use a password manager app on your smartphone, it may be vulnerable to package name spoofing, which would allow the password manager’s autofill feature to enter your login credentials on a spoofed web form. This vulnerability applies to popular apps from LastPass, Dashlane, Keeper, and 1Password.
I have been an advocate for password managers. They are part of the solution to creating long (20 characters?) random passwords that are unique to hundreds of sites and services. I use LastPass myself. The good news: when you use your password manager from computer on a web browser, when a site is visited for the first time the password manager creates an association between its domain (verified by its digital certificate) and the credentials used to access it.
But the phone apps use a different association method that is not as strong, and can be circumvented through a spoofing attack. This exploit takes advantage of the auto-fill feature to steal your credentials. Personally, I have never set up the phone app because I had security concerns. It is too easy to lose a phone, too easy to hijack the phone contents through a Bluejacking or BlueBorne attack. Turns out my paranoia was well-founded.
The researchers who discovered this flaw reported it to the password manager developers, and solutions are in the works. For now the easiest work-around is simply to disable the auto-fill function on your password manager app, or be more vigilant about the places you are logging into. In any event, I recommend you continue to use your password manager app, as it is a better solution than reusing weak, memorized passwords.