This article describes the issue when using the Ektron Captcha server control on Pagebuilder.  When using the control on a Pagebuilder page it does not prevent the form submission as part of the validation process.

This issue has been resolved in the following CUs.

9.2 SP2 Site Update
Site Update 3 (November 28, 2017)
EKTR-312: Captcha Not Working With Pagebuilder Form Widget

9.10 SP3 Site Update
WARNING: Back up your database before installing any software patch.
NOTE: Each update includes all previous cumulative updates for 9.10 SP3.

Update 41 (November 28, 2017)
EKTR-328: Captcha Not Working With Pagebuilder Form Widget

For more information on installing updates please see here.