IPFire < v2.29 Stored XSS via Time Constraint Rule URL Filter

IPFire versions prior to 2.29 (Core Update 198) contain a stored cross-site scripting (XSS) vulnerability that allows an authenticated attacker to inject arbitrary JavaScript code through the SRC, DST, and COMMENT parameters when creating a time constraint rule. When a user adds a time constraint rule the application issues an HTTP POST request to /cgi-bin/urlfilter.cgi with the MODE parameter set to TIMECONSTRAINT and the source hostnames/IPs, destination, and remark provided in the SRC, DST, and COMMENT parameters respectively. The values of these parameters are stored and later rendered in the web interface without proper sanitation or encoding, allowing injected scripts to execute in the context of other users who view the affected time constraint entry.