A Cross-site Scripting (XSS) vulnerability in Juniper Networks Junos OS J-Web allows an attacker to construct a URL that when visited by another user enables the attacker to execute commands with the target's permissions including an administrator. This issue affects: Juniper Networks Junos OS 12.3 versions prior to 12.3R12-S19; 15.1 versions prior to 15.1R7-S10; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R2-S10 18.4R3-S9; 19.1 versions prior to 19.1R2-S3 19.1R3-S6; 19.2 versions prior to 19.2R1-S8 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-S2; 20.2 versions prior to 20.2R3-S2; 20.3 versions prior to 20.3R3; 20.4 versions prior to 20.4R2-S2 20.4R3; 21.1 versions prior to 21.1R1-S1 21.1R2; 21.2 versions prior to 21.2R1-S1 21.2R2.