Is WuCai - Highlight and Note safe?

WuCai sends the URL and title of every page you visit to its servers while you are logged in.

On each page load and tab switch, WuCai's content script reports the current page's full URL and title to the vendor backend to look up any saved highlights for that page. The request includes your account token and runs for every non-blacklisted page regardless of whether you have highlights there, so it amounts to a continuous feed of your browsing URLs to WuCai while signed in.