Attackers interested in getting the most bang for their buck focus on ubiquitous software. Webkit has a significant share of the PC and Mac markets because of its inclusion into Google’s Chrome and Apple s Safari browsers. A host of other applications such as Yahoo! Messenger, MSN Messenger, iTunes, and even RealPlayer use Webkit to render rich text formatting and interactive content. The Safari browser and BlackBerry both fell because of flaws in Webkit. Not all developers patch their code quickly; developers will be hard pressed to keep up with vulnerability discoveries.
Source: https://threatpost.com/weaknesses-webkit-becoming-problematic-082811/75586/