Xpdf is "an open source viewer for Portable Document Format (PDF) files. (These are also sometimes also called 'Acrobat' files, from the name of Adobe's PDF software.) The Xpdf project also includes a PDF text extractor, PDF-to-PostScript converter, and various other utilities." Secunia Research has discovered some vulnerabilities in Xpdf, which can be exploited by malicious people to compromise a user's system.
http://www.securiteam.com/unixfocus/6M0012AKAW.html
