Google, ETH, and IBM released a paper about how 59.1% of users are running the most up-to-date browser available to them, and that a decent number of people were not running fully-patched versions. From a security and standards-compliance position, this is bad.
How can this be dealt with? One suggestion made by the authors was to have an integrated part of the browser's GUI that specified how "expired" their browser is. That's a good idea, but we all know that users are slow on the pick up in terms of upgrading, as the paper points out. So what to do?
Well, what happened if a prominent warning came up on various web sites that a person visited, telling them that their browser was out of date? If instructions were included on how to update, would people actually update their browsers? If some prominent web sites had this info, it is quite possible. But having to keep track of all that user agent info would be a pain in the rear for each site.
And that is where a web service would come in handy. If there was a simple RESTful API for people to hit where the user agent for a browser could be sent to and return, in JSON, whether the browser was outdated or not, how outdated by time it was, and the severity of how outdated it is, it would make it easer for sites to include such information. One could go as far as to include a link that went to the proper page listing instructions on how to update their browser.
Do people think that would actually be useful?