Eight percent of Wi-Fi networks in central London use no encryption at all.
The company has been ordered to refund all customers and pay a £50,000 fine.
The app was removed from Apple's App Store two months ago for undisclosed reasons.
The app provides users with nearby Democrats' first names, ages, genders and home addresses.
The company also says a third of Android apps are compromised with malware.
Near Field Communication vulnerability on Android phones demonstrated at the Black Hat 2012 conference.