Adobe Reader is one of the most widely-installed programs, used by millions to read PDF files (although there are a number of alternative PDF readers available). That makes it an attractive target for attackers. A critical security vulnerability in the software, which was warned about three weeks ago, could allow attackers to take control of affected computers.
Adobe has announced that they will be releasing an update to fix the flaw this Tuesday. The updates apply not only to Windows versions of Adobe Reader but also to Mac and UNIX versions. Read more here: