Myki is a decentralized password manager which means that all data available to the add-on is received by the mobile app.
We, at Myki, do not store or process your sensitive data (and have no desire to) and as such, all user data available is stored within the mobile app and shared with the extension on a need-to-know basis.
When the mobile app is paired with the browser extension, all data exchanged with the mobile app is end-to-end encrypted using 256-bit AES encryption.
While paired, metadata about the logins, payment-cards, and notes are shared with the extension. This metadata may be temporarily stored within the browser to insure uninterrupted usage between browser restarts.
During a login attempt to any website, a request is sent to the user's mobile app, which if approved will transmit the sensitive data of that specific account back to the browser for this request only.
If the extension is set as "Trusted" by the user, then a copy of user's sensitive data is securely transferred from the user's mobile app to the extension. This data is held in the Myki extension without being stored meaning the data is not stored within the browser and is not even available between browser restarts.
Note that this statement does not cover related products and services so you should inspect privacy policies of those as applicable.