Thread:Extension talk:ConfirmEdit/The current version of this extension is not compatible with 1.20

That includes the version of the extension that is bundled with 1.20.

If you set $wgCaptchaClass = 'FancyCaptcha' in your LocalSettings.php you will get an HTTP 500 error if you attempt any operation involving a captcha such as creating a new account. If you look in FancyCapthca.class.php you will see it includes a call to getWikiId. The FSFileBackend class does not have that method in 1.20, although the trunk version does. The Apache error_log confirms that the failure is due to an attempt by FancyCaptcha.class.php to call FSFileBackend::getWikiId.

I am currently using the 1.19 version of this extension with 1.20 without any problems.