The product uses external input to determine the names of variables into which information is extracted, without verifying that the names of the specified variables are valid. This could cause the program to overwrite unintended variables.
For example, in PHP, extraction can be used to provide functionality similar to register_globals, a dangerous functionality that is frequently disabled in production systems. Calling extract() or import_request_variables() without the proper arguments could allow arbitrary global variables to be overwritten, including superglobals.
Similar functionality is possible in other interpreted languages, including custom languages.
Time of Introduction
Technical Impact: Modify application data
An attacker could modify sensitive data or program variables.
This code uses the credentials sent in a POST request to login a
//Log user in, and set $isAdmin to true if user is an
The call to extract() will overwrite the existing values of any
variables defined previously, in this case $isAdmin. An attacker can
send a POST request with an unexpected third value "isAdmin" equal to
"true", thus gaining Admin privileges.