A reflected Cross-site Scripting (XSS) vulnerability in J-Web of Juniper Networks Junos OS allows a network-based authenticated attacker to run malicious scripts reflected off J-Web to the victim's browser in the context of their session within J-Web. This may allow the attacker to gain control of the device or attack other authenticated user sessions. This issue affects: Juniper Networks Junos OS All versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R3-S9; 19.1 versions prior to 19.1R3-S6; 19.2 versions prior to 19.2R3-S3; 19.3 versions prior to 19.3R2-S6 19.3R3-S3; 19.4 versions prior to 19.4R3-S5; 20.1 versions prior to 20.1R3-S4; 20.2 versions prior to 20.2R3-S2; 20.3 versions prior to 20.3R3; 20.4 versions prior to 20.4R3; 21.1 versions prior to 21.1R1-S1 21.1R2.