The Britain blog Comparitech called "Most Used Words" a "privacy nightmare." In addition to giving the app permission to read and analyze all of your Facebook status updates, users gave it permission to access their full name, age, date of birth, profile photo, hometown, current city, their entire friends list, everything they've ever "Liked," all of their photos and photos they are tagged in, IP address and information about the device they were using when they clicked "accept."
If you've already given Vonvon your information and are regretting it, there's no way to take it back. PCMag has some good tips for how to adjust your privacy settings on Facebook. Basically, think long and hard about what you're sharing before you allow any third-party app to access any of your personal information, and whether it's worth sharing all of that for a quiz result or Facebook status.