FireEye researchers have discovered a rapidly growing class of mobile threats represented by a popular ad library affecting apps with over 200 million downloads in total. This ad library, anonymized as "Vulna", is aggressive at collecting sensitive data and able to perform dangerous operations such as downloading and running new components on demand. Vulna is also plagued with various classes of vulnerabilities that enable attackers to turn Vulna's aggressive behaviors against users. FireEye has coined the term “vulnaggressive” to describe this class of vulnerable and aggressive characteristics. Most vulnaggresive libraries are proprietary and it's hard for app developers to know their underlying security issues. Legitimate apps using vulnaggresive libraries present serious threats for enterprise customers. FireEye has informed both Google and the vendor of Vulna about the security issues and they are actively addressing it.