On Zyxel ATP200, ATP500, ATP800, USG20-VPN, USG20W-VPN, USG40, USG40W, USG60, USG60W, USG110, USG210, USG310, USG1100, USG1900, USG2200-VPN, ZyWALL 110, ZyWALL 310, ZyWALL 1100 devices, the security firewall login page is vulnerable to Reflected XSS via the unsanitized ‘mp_idx’ parameter.
packetstormsecurity.com/files/152525/Zyxel-ZyWall-Cross-Site-Scripting.html
seclists.org/fulldisclosure/2019/Apr/22
www.exploit-db.com/exploits/46706/
www.securitymetrics.com/blog/Zyxel-Devices-Vulnerable-Cross-Site-Scripting-Login-page
www.zyxel.com/support/reflected-cross-site-scripting-vulnerability-of-firewalls.shtml