Mozilla 1.1 and earlier, and Mozilla-based browsers such as Netscape and Galeon, set the document referrer too quickly in certain situations when a new page is being loaded, which allows web pages to determine the next page that is being visited, including manually entered URLs, using the onunload handler.

Netscape 6 and Mozilla 1.0 RC1 and earlier allows remote attackers to determine the existence of files on the client system via a LINK element in a Cascading Style Sheet (CSS) page that causes an HTTP redirect.