The CheckLoadURI function in Mozilla Firefox 1.8 lists the about: URI as a ChromeProtocol and can be loaded via JavaScript, which allows remote attackers to obtain sensitive information by querying the browser's session history.
Exploitability
AV:NAC:LAu:NImpact
C:PI:NA:N5/AV:N/AC:L/Au:N/C:P/I:N/A:N