For over two decades, and Adobe Reader (now Acrobat Reader) were the twin pillars of the internet experience. If you wanted to watch a video, play a game, or read a professional document, you likely relied on these two pieces of software.
The deep integration between Flash and Reader created a significant security surface. Vulnerabilities found in Flash Player often automatically affected Adobe Reader. Flash Player end-of-life Impact in Reader and Acrobat adobe flash player adobe reader