"Adobe’s Flash Player software is on 99 percent of Internet-connected desktops, offering up multimedia and video capabilities on a multitude of popular Web sites such as YouTube. But the Adobe Flash platform has been beset by a rash of security problems that give intruders potential access to computers running the software.Issues have included one recent vulnerability described as "frighteningly bad" by a security expert.
Technologists, however, disagree on the severity of Flash’s weaknesses. Some say Flash is merely a victim of its own success, attracting attention from those with bad intentions but being no worse off than other software platforms when it comes to its inherent security. An alternate opinion is that Adobe simply lacks tight security practices in its internal development procedure and so has become a preferred vector for cyberthieves." – Content courtesy of Adobe Flash’s security woes: How to protect yourself
You may also like to read