I'm affraid that your PC is infected by Maleware... Try download a Tool like "ad aware" or "malewarebytes" and let that check your system...
Looks like something is hijacking your steam clients browser. Where exactly did you click before this popped up?
Yeah, I think that it's also malware. But, what is the link in the steam browser? A link of Sector 3 or that site link ? (I cannot read it, and I am NOT interested in that website ) Check also that you use the DNS IP addresses of your internet provider or Google (and not a malware DNS IP address) En français: Je crois aussi que c'est un malware (essaie d'installer Malwarebytes (ou quelque chose du genre) pour résoudre le problème). Mais, le lien en question dans le navigateur de Steam, c'est un lien de Sector 3 ou le lien du site même (ou un lien qui n'existe pas)? Si c'est un lien qui n'existe pas, il se peut que tes serveurs DNS ont été modifiés. Il faut donc vérifier l'adresse IP de tes serveurs DNS. Normalement, il devrait être ceux de ton fournisseur d'Internet (FAI) ou par exemple ceux de Google.
The code behind advertising tools like that normally choose adverts or subject matter based upon the users own browsing history. This is in order to try to maximise the users chances of clicking on it. I suspect if you stop looking at porn the problem will go away.
S3E bring us this new feature meanwhile load the track, especially usefull with large ones like nordschleife
This looks more like "Female ware" to me Definitely agree that Malware Bytes is a good program to use though. The free version is more than sufficient to find those bad bugs hidden away. That with Windows Defender and you are good to go.