I see the confusion here. Jaguar, the way you describe it above is not exactly how ads work. If they are malware, which I believe they are based on everything you've said thus-far, it's not that they are "using tvmaze" as a conduit for their ads without tvmaze knowing, they are using your computer/browser and it has nothing to do with tvmaze security. You definitely need to find and rid this malware before you will stop seeing these ads.
You might also try the simple step of trying a different browser for a while and see if that solves it. If they go away, that would confirm that it is your computer, and perhaps help you narrow it further to something like a Firefox plugin. As before, I still recommend clearing your cache and cookies on Firefox as a first step. Hope you get this figured out!

