Many times on your desktop or even on smartphone we just hit next button for logging using third party like social media or web applications. Without knowing the back details of it.
These logging allows to use your email id, name but unknowingly it access your photo, messages, even contacts sometimes. Many Web applications or website which we are using by the time get damaged or rogue. If you have already logged in with these types of logging it is big threat to your privacy on that account.
As a threat you may see spam content or messages on your account’s home page or timelines, which are sometimes shared publically, it may happen that unknowingly the spam content get travelled through your contact list , basically you can be the victim for hacking using third party login.
To avoid this the preliminary action you can take is, do not login through your personal accounts to such web apps.
There are ways to control the application from setting you can rightly use it like permission control. What permissions to give to the particular app.
Or simply uninstall it and use it from authorized service provider.