reCaptcha and privacy issues With reCaptcha, a JavaScript element is included in the source code and then the tool runs in the background and analyzes user behavior. Website visitors are not made aware that an analysis is taking place. This leads to the first privacy issue:
Lack of transparency

For the analysis of behavior, personal data such as:

IP address (e.g., 192.168.178.11)
Referrer URL (the address of the page from which the visitor came)
Operating system info (the software that enables your computer to operate.
Cookies, if applicable
Mouse movements and keyboard strokes
Dwell time
user device settings (e.g. language settings, location, browser, etc.)

forwarded to Google.

Website users are usually not at all aware that they are being monitored in the background. Google also keeps a low profile about what data is collected and how it is used.