This exploit was picked up by Defused as early as October 20th where it was thought to be a variant of CVE-2022-40684. However, Fortinet have confirmed that this is a new vulnerability and have assigned this CVE to the vulnerability. This vulnerability takes advantage of both a path traversal (/api/v2.0/cmdb/system/admin%3f/../../../../../cgi-bin/fwbcgi) and an auth bypass via the cookie CGIINFO.
Fortinet offer little information within their disclosure, and until today there was no patching information as mentioned within watchTowr's article. The infosec community has collated some IOC's which can be found here. This vulnerability has been actively exploited to create a new administrative user, any instances of Fortiweb that have exposed the web GUI to the internet should be considered compromised.