I have now installed AdGuard for Safari, thanks for the tip guys. It's pretty obvious that the Flash Player Installer is linking to another site other than Adobe so I didn't fall for it.
The worst one that I saw was a pop-up that appeared to be from my ISP which is a telco. They copied all the logos, knew how many years I was a subscriber and promised a free cell phone for answering a survey. At the end they ask for a credit card to cover the cost of shipping. That's when I knew it was a scam. Then I looked into the source code of the page and found the domain was registered in Panama. The name of the ISP is possible to get from the DOM in the browser, but having subscriber information must mean that there was a hack at the company.