This plugin finds any CAPTCHA images that appear on a HTML document. The crawl is performed by requesting the document two times, and comparing the image hashes, if they differ, then they may be a CAPTCHA.
This plugin doesn’t have any user configured options.
For more information about this plugin and the associated tests, there’s always the source code to understand exactly what’s under the hood:
Plugin source code
Unittest source code
This plugin has no dependencies.