How to client-side detect when a page is bookmarked?

Question

Is it possible to detect when a page is bookmarked within the browser, using Javascript?

Answer 1

Most browsers will not let you detect when a page is bookmarked because this would be another vector for Browser History Mining exploits.

If malicious code could tell what websites you've used then, for example:

1. At best, they'd know things about you that you might wish to keep private.
2. They could use that information to target you with embarrassing ads or to target your kids with irresistible ads.
3. They could target you with much more effective phishing attacks -- since they'd know services, banks, etc. you use online.

It is for this reason that the HTML spec has long required that:

The actual (history) entries are not accessible from script.

It follows that bookmarks are an even more lasting form of history, so they would not be allowed either.
Indeed whenever side-channel history-mining exploits (like the CSS :visited vulnerability) became known, the appropriate specs are adjusted and security-conscious browsers move to block the privacy hole.