Keys for Safari does not collect any personal information whatsoever on users.
Why does Safari caution me that Keys has permissions to read sensitive information from webpages including passwords, phone numbers, and credit cards on all sites and has access to my browsing history?
Although Keys for Safari does not attempt to collect any of this sensitive data, it must run Javascript on the webpages you visit in order to function. Hence, Apple cautions its users that a malicious extension with these permissions could read sensitive information from users. Apple requires, however, that developers submit government-issued photo ID. For users' peace of mind, the Keys for Safari source has been made publicly viewable in this repository.
If you have any further questions about the privacy policy, feel free to email me at keys4safari@gmail.com.