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.

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.

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 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.

Netscape Communicator 4.73 and earlier allows remote attackers to cause a denial of service or execute arbitrary commands via a JPEG image containing a comment with an illegal field length of 1.

The byte code verifier component of the Java Virtual Machine (JVM) allows remote execution through malicious web pages.

Java in Netscape 4.5 does not properly restrict applets from connecting to other hosts besides the one from which the applet was loaded, which violates the Java security model and could allow remote attackers to conduct unauthorized activities.