A German government agency on Wednesday warned iPhone, iPod touch and iPad users about serious vulnerabilities in Apple's mobile operating system.

According to The Bundesamt fr Sicherheit in der InformationstechnikGerman (BSI) or Federal Office for Information Security, Apple's iOS operating system has "two critical weak points for which no patch exists".

The BSI warned against opening PDFs on Apple's mobile devices and suggested users avoid downloading PDFs or anything else from websites they did not trust.

The warning covers iPhones using iOS versions 3.1.2-4.0.1, iPod touches using iOS 3.1.2.-4.0 and iPads using iOS 3.2-3.2.1.

Georg Albrecht, a spokesman for Apple in Germany, briefly told The Associated Press that the company is looking into the issue: "We know these reports and are investigating them."

The warning, in German, is available here.

The same vulnerability allows Apple's devices to be jailbroken by simply visiting a website.