No current issues were found in the code review. although the plugin has not been maintained and noting possible data protection issues as described below.
Reason for the 'Potentially unsafe' result
The plugin has been given this recommendation at the tester's discretion:
From the WordPress.org plugin page the plugin does appear unmaintained (“This plugin hasn’t been tested with the latest 3 major releases of WordPress.” and “Last updated:8 years ago”). Using alternatives is therefore recommended, and if used, the plugin should be kept under review for any issues that arise with future WordPress-related changes.
The plugin also sends the user IP address with the Google Captcha API check. This is optional for the API, so would be better if left out to avoid data protection concerns.