Improper directory permissions in the Hotspot Shield VPN client software for Windows 10.3.0 and earlier may allow an authorized user to potentially enable escalation of privilege via local access. The vulnerability allows a local user to corrupt system files: a local user can create a specially crafted symbolic link to a critical file on the system and overwrite it with privileges of the application.

Hotspot Shield runs a webserver with a static IP address 127.0.0.1 and port 895. The web server uses JSONP and hosts sensitive information including configuration. User controlled input is not sufficiently filtered: an unauthenticated attacker can send a POST request to /status.js with the parameter func=$_APPLOG.Rfunc and extract sensitive information about the machine, including whether the user is connected to a VPN, to which VPN he/she is connected, and what is their real IP address.