IPFire < v2.29 Stored XSS via DNS Creation (proxy.cgi)

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 TLS_HOSTNAME, UPSTREAM_USER, UPSTREAM_PASSWORD, ADMIN_MAIL_ADDRESS, and ADMIN_PASSWORD parameters when adding a new DNS entry. When a user adds a DNS entry, the application issues an HTTP POST request to /cgi-bin/dns.cgi and these values are provided in the corresponding parameters. The values 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 DNS configuration.