As far as I can tell, it's a mistake on the site.

As of last night, the plugin checker wants you to have 21.0.0.226 (see linked screenshot), but that update is, as far as I can tell, only for Mac at this point, and not security related.

For Windows, 21.0.0.213 still is the latest. Hopefully they'll fix it before we get a dozen more questions!

https://support.cdn.mozilla.net/media/uploads/images/2016-05-04-23-07-58-3e1683.png

looks fixed already: https://www.mozilla.org/en-US/plugincheck/

Not fixed for me, but I think that's a CDN issue, if I add a random parameter then I do get a more updated file compared with the one I get in normal browsing:

https://plugins.mozilla.org/en-us/plugins_list.json

Access-Control-Allow-Origin: * Cache-Control: max-age=3600 Connection: Keep-Alive Content-Type: application/json Date: Thu, 05 May 2016 15:20:36 GMT Expires: Thu, 05 May 2016 16:20:36 GMT Keep-Alive: timeout=5, max=1000 Server: Apache Strict-Transport-Security: max-age=31536000; includeSubDomains Transfer-Encoding: chunked Vary: User-Agent, Accept-Encoding Via: Moz-Cache-zlb1 X-Backend-Server: plugins2.webapp.phx1.mozilla.com X-Cache-Info: cached X-Powered-By: PHP/5.3.3 x-frame-options: DENY

Works for me now - whereas last night it was red flagging 21.0.0.213

Thanks all, definitely fixed now.

Thank you. problem is solve!