said by FF4m3 :Rid yourself of Adobe: New Firefox 19.0 gets JAVASCRIPT PDF viewer:
Mozilla's Firefox web browser now includes a built-in PDF viewer - allowing users to bin plugins from Adobe and other developers.
The move to run third-party PDF file readers out of town comes after security holes were discovered in closed-source add-ons from FoxIt and Adobe. The new built-in document viewer is open source, just like Firefox, and is written in JavaScript.
And why won't these open source PDF readers become targets of hackers? If they gain large numbers of users(like they will when included in Firefox) they will also become targets.