This one line HTML Email message will hang the Eudora and Netscape Messanger
Email readers:
<html> <script> while(1) alert("Help, I am caught in an infinite loop!"); </script> </html>
The hang occurs when the Email message is read. The embedded JavaScript
program is automatically executed and puts up a continuous stream of alert
boxes on the screen. In both Email readers, there doesn't seem to
be any method of easily stopping the alert boxes. CTRL-ALT-DEL
is required to shutdown the hung Email reader.
Worse yet, the next time Email is read, Eudora and Netscape Messanger will
hang again on the same Email message if the message preview pane is turned on.
This message will likely permanently disable the Email reader. To
fix the problem
requires a person with technical knowledge to manually edit the "in" box message
file and delete the message with the JavaScript infinite loop.
Moral of the story, Email readers should never, ever automatically execute
programs embedded in Email messages even if these programs are written
in supposely safe programming languages like JavaScript, VBScript, and
Java.
For a list of ways to crash a Web browser or Email reader
using JavaScript, Click Here