Buffer overflow in the sun.awt.windows.WDefaultFontCharset Java class implementation in Netscape 4.0 allows remote attackers to execute arbitrary code via an applet that calls the WDefaultFontCharset constructor with a long string and invokes the canConvert method.

Netscape Communicator does not properly prevent a ServerSocket object from being created by untrusted entities, which allows remote attackers to create a server on the victim's system via a malicious applet, as demonstrated by Brown Orifice.

Netscape Communicator 4.0 through 4.79 allows remote attackers to bypass JVM security and execute arbitrary Java code via an applet that loads user-supplied Java classes.

Netscape Communicator and Navigator 4.04 through 4.74 allows remote attackers to read arbitrary files by using a Java applet to open a connection to a URL using the "file", "http", "https", and "ftp" protocols, as demonstrated by Brown Orifice.

The POP3 mail client in Mozilla 1.0 and earlier, and Netscape Communicator 4.7 and earlier, allows remote attackers to cause a denial of service (no new mail) via a mail message containing a dot (.) at a newline, which is interpreted as the end of the message.

Netscape Communicator 4.x allows attackers to use a link to steal a user's preferences, including potentially sensitive information such as URL history, e-mail address, and possibly the e-mail password, by redefining the userpref() function and accessing the prefs.js file, which is stored in a directory with a predictable name.

Mozilla 0.9.6 and earlier and Netscape 6.2 and earlier allows remote attackers to steal cookies from another domain via a link with a hex-encoded null character (%00) followed by the target domain.