Generally speaking it's a good idea to keep your version of Adobe Flash up to date (along with Java, for that matter) but it appears that many people around the world are currently vulnerable to the latest exploit doing the rounds. Two exploit kits, named Angler and Magnitude, contain the ability to deploy ransomware onto a PC, forcing the user to hand over money to regain control. The exploit was fixed by Adobe last week, but it turns out that there are a large proportion of computers that have not updated to the latest version (probably because of the constant pop-ups that annoy everyone.)
As pointed out by the fine folks at Bitter Wallet, Chrome users will have Flash updated to the latest version, but everyone else will need to update manually. You can check to see if you have the latest version of Flash by clicking here. If you aren't up to date, or just want to make sure, you can get the latest version of Flash by heading over to the Adobe Flash download page.