I was reading this article and, in my opinion, it got the facts right but their conclusion is backwards:
Meanwhile, whilst this particular unlock is the simplest, it also carries with it element of risk that you’re going to want to protect yourself against.
What? No that’s not the correct conclusion. A conclusion that would make more sense is that everybody is at risk until this PDF hole is patched by Apple. Jailbroken and non-jailbroken phones alike.
However, if you have jailbroken your phone, you have access to a fix now as described in the article reference above:
1. Open Cydia
2. Install “PDF Loading Warner”
3. Reboot your phone