View Joomla, Drupal, Wordpress version on filesystem

# Joomla! 1.0.x
<root>/includes/version.php
# Joomla! 1.5.x
<root>/libraries/joomla/version.php
# Joomla! 1.6.x
<root>/libraries/joomla/version.php
# Joomla! 2.5.x
/libraries/cms/version/version.php

# Drupal:
<root>/includes/bootstrap.inc
<root>/CHANGELOG.txt

# Wordpress:
<root>/wp-includes/version.php