Wireshark released a new version (1.0.4). The new version includes a number of security fixes. For details, see http://www.wireshark.org/news/20081020.html .

Just by its nature of including a large number of protocol parsers, Wireshark is a somewhat risky program. To mitigate the risk, collect traffic using a simpler program like tcpdump, and later analyze the traffic in wireshark using a low privilege account.