While adding general comments is very useful, some programmers tend to leave important data, such as: filenames related to the web application, old links or links which were not meant to be browsed by users, old code fragments, etc.
An attacker who finds these comments can map the application's structure and files, expose hidden parts of the site, and study the fragments of code to reverse engineer the application, which may help develop further attacks against the site.
Time of Introduction
Technical Impact: Read application
The following comment, embedded in a JSP, will be displayed in the
resulting HTML output.
Example Languages: HTML and JSP
<!-- FIXME: calling this with more than 30 args kills the
JDBC server -->