Another day, another Office vulnerability, it seems. This time around, a flaw has been discovered in Microsoft's PowerPoint program that could result in infection by a nasty trojan. The Trojan, carried through PowerPoint files, will try to install other malicious software on the machine once it has compromised it. There's currently no patch available for the flaw, but anti virus companies are already working to protect people:

In the absence of an appropriate fix from Microsoft users are advised to employ up-to-date anti-virus software to block infection while also avoiding the temptation to open unsolicited PowerPoint files from trusted sources
Although a bit of common sense helps prevent most infections, they still do occur, so it is always best to be cautious when dealing with files you find “wandering around the Internet”.