Transmission through 2.92 relies on X-Transmission-Session-Id (which is not a forbidden header for Fetch) for access control, which allows remote attackers to execute arbitrary RPC commands, and consequently write to arbitrary files, via POST requests to /transmission/rpc in conjunction with a DNS rebinding attack.
bugs.chromium.org/p/project-zero/issues/detail?id=1447
github.com/transmission/transmission/pull/468
lists.debian.org/debian-lts-announce/2018/01/msg00020.html
security.gentoo.org/glsa/201806-07
twitter.com/taviso/status/951526615145566208
www.debian.org/security/2018/dsa-4087
www.exploit-db.com/exploits/43665/