sensible-browser in sensible-utils before 0.0.11 does not validate strings before launching the program specified by the BROWSER environment variable, which allows remote attackers to conduct argument-injection attacks via a crafted URL, as demonstrated by a --proxy-pac-file argument.
https://www.debian.org/security/2017/dsa-4071
https://usn.ubuntu.com/3584-1/
https://lists.debian.org/debian-lts-announce/2017/12/msg00012.html