Stefano Di Paola y Giorgio Fedon have discovered various vulnerabilities in Adobe Acrobar Reader's plugin. They presented them at CCC's Congress with a presentation on Vulnerabilities in Web applications that use AJAX.
The original advisory can be found here.
You can find more information on this vulnerability here.
Affected sistems(known at the moment):
Version 6.0.1 for Windows via Internet Explorer 6
Version 7.0.8 for Windows via Firefox 18.104.22.168.
Other versions may also be affected.
Thanks to Mario Ballano and Pedro Montoya.