Updated LinkedIn's country subdomain SSL certificate has expired – apparently as of about noon GMT today.
According to the sslscan certificate testing tool, us.linkedin.com and all its altnames were no longer valid at the time of publication.
The certificate issuer is DigiCert SHA2 Secure Server CA.
The certificate for the naked domain, www.linkedin.com, is separate – and still kosher until noon GMT on December 14 next year.
She said "a large percentage" of web users visiting a site they have been to before, especially a trusted site, will "click through" certificate warnings.
She said having an invalid certificate warning "trains users that it's safe to click through those warnings" and "the next one might be a real attack".