Since two YT community members have seen this, I thought it was worth posting a message about. A new form of Adware (and sometimes Virus or Spyware) called browser hijacking is getting very common. If you go to certain sites, you'll see that words are highlighted, and if you hover over them, or click on them, it will take you to some completely unrelated spam site. We've all seen sites where this happens as part of their advertising, but most of the time now, it's because your browser has been hijacked, and it's stuffing those links into the page you see. The page you see isn't what the site sent to you though.
YT doesn't have any ad links like that. The community doesn't want ads like that, so we don't have them. The site is supported only by donation and the fact that we sell parts and manuals. So if you see links in posts here, you need to fix it on your browser.
The ones I've searched up, are put into your PC by what is called "Extensions" (may be Add-ins or Add-ons in your browser) of the browser. Extensions are little applications that are "supposed" to enhance your browsing experience. Some do, there are special extensions that do things like give you options to change a sites appearance, something that can be useful if you have trouble with your eyesight. Normally, you install these on purpose. But the hijack extension usually isn't something you meant to do, for example, on a bad website or link from an email, it may ask a question that seems safe, it wants to add something to your browser, yet you are really giving that site the right to upload an extension which may be adware. If your browser has extensions enabled, it hijacks your sessions to other sites running known types of software.
These hijack programs can be smart about how they insert the adware into the page you view. They know several different types of software used by sites across the net, so they can "intelligently" change the words or links. That's why you don't see links at every site you go to after your browser is hijacked. It's only going to change pages for sites running the software it knows. If it knows wwwboard (the forum software we use on Classic view), then posts displayed to you will have those links in it, usually it's forum posts (or anything that has User-supplied content, like blog comments) where these guys do their dirty work, because that is easy to do without being noticed too much.
Another example of this "intelligence" of these hijackers, is one that looks just like a facebook link only from a site that isn't facebook. When you click it, it's asks you a question to which if you respond Yes, it installs a hijacker that will then become active when you read facebook posts. Of course this has nothing to do with facebook, it just "knows" facebook pages and can change them from what facebook sent you, to what the extension "wants" you to see. There are hundreds of such programs out there.
My personal way of handling this type of thing is based on the fact that I don't want ANY "enhanced" browsing, I want pages I visit to be displayed exactly how the website sends it to me. So I never turn browser extensions on. If I get a message asking if I want to install something, I say "No" which means my browser won't permit the hijacker to be installed.
If you want "extensions" on, the safest way to deal with it, in my opinion, is to know what extensions you've intentionally installed and check them occasionally, to make sure that there aren't any new ones. Then specifically disable and delete any you don't recognize.
One other thing I'd like to mention, some of these extensions are installed by clicking on links that friends have sent you in email. My opinion is that if a friend "sends" me a link, they better explain what it is and why they want me to follow it. The big free email sites tend to have a lot of account stealing going on now, so it may not be your friend that actually sent the link. I've seen this happen to a couple of friends lately, I received messages from them with suspicious links and knew right away, someone had stolen their email account. If you click on those links, you can get viruses, spyware and adware installed on your PC.
Sorry for the length of this, but I couldn't figure out how to shorten it.
P.S. at the last minute, I noticed there are software security programs out there which will scan an remove this issue from your PC.