reCAPTCHA v1 was deprecated as of March 31, 2018. To deter spam submission through storefront forms, BigCommerce now supports Google reCAPTCHA v2 challenges, to distinguish human customers/visitors from automated bots. We recommend that all storefront themes take advantage of this upgraded bot detection.
If you have based your theme on a theme/version that already incorporates reCAPTCHA v2, you do not need to take any further action. Compliant themes/versions currently are listed in Updating Themes with reCAPTCHA V2 (Knowledge Base).
To add reCAPTCHA v2 support to a theme, update script references in three template files. You can find them in the following subdirectories of the {theme-name}/templates/ directory:
See PR #951 in the Cornerstone GitHub Repository to see differentials for each file that needs to be modified.
It is possible to add reCaptcha to the Login template. See the Forms object for details.