Teltonika RUT9XX routers with firmware before 00.05.01.1 are prone to cross-site scripting vulnerabilities in hotspotlogin.cgi due to insufficient user input sanitization.
http://seclists.org/fulldisclosure/2018/Oct/29
http://packetstormsecurity.com/files/149781/Teltonika-RUT9XX-Reflected-Cross-Site-Scripting.html