Revealing system data or debugging information helps an adversary learn about the system and form a plan of attack.
An information leak occurs when system data or debugging information leaves the program through an output stream or logging function.
Example: The following code prints CGI environment variables to a web page:
...
HTP.htmlOpen;
HTP.headOpen;
HTP.title ('Environment Information');
HTP.headClose;
HTP.bodyOpen;
HTP.br;
HTP.print('All CGI Environment Variables: ');
OWA_UTIL.print_cgi_env;
HTP.br;
HTP.bodyClose;
HTP.htmlClose;
...
[1] Standards Mapping - OWASP Top 10 2007 - (OWASP 2007) A6 Information Leakage and Improper Error Handling
[2] Standards Mapping - Security Technical Implementation Guide Version 3 - (STIG 3) APP3620 CAT II
[3] Standards Mapping - Common Weakness Enumeration - (CWE) CWE ID 497
[4] Standards Mapping - Web Application Security Consortium 24 + 2 - (WASC 24 + 2) Information Leakage
[5] Standards Mapping - Payment Card Industry Data Security Standard Version 2.0 - (PCI 2.0) Requirement 6.5.5
[6] Standards Mapping - Payment Card Industry Data Security Standard Version 1.2 - (PCI 1.2) Requirement 6.5.6