As part of my research into Gadget Chains and PHP Object Injection, I discovered an unsafe deserialisation vulnerability in The Marketer OpenCart module.
There are Gadget Chains available in Opencart - including a few that I found and submitted to the PHPGGC project:
https://github.com/ambionics/phpggc/pull/199 (not yet merged).
The vulnerability in The Marketer module, combined with these Gadget Chains, allows remote unauthenticated RCE so it got a very high CVSS score.