The application (applet) is already downloaded, and it is only using that domain in an internal HTTPS request, to get/send business data, not to download additional Jars, JNLPs, etc.
Again, this started to happen after updating my JRE to 8u25.
But it might also be the case, that Java 7 did not verify the hostname in the certificate at all, while Java 8 has incomplete verification. Previous version of Java 7 and 8 don't have this issue (SSL certificate restrictions for CN in a different casing). Yes, hitting "Continue" allows the application to load without problems, but the problem is that I am the developer of this application, and it is not good for the business that this app keep asking the customer if he/she trusts the site/app.
Anyway, this solved the issue, and now we receive a gentle information message about the domain: If you trust the certificate and the website you are accessing, hit Continue to get past this message. I also doubt it is case sensitive, but to be sure, I'll search some more info about it.
Action to take If you encounter this issue, you see the list of files and folders that failed import in your job completion report.
In some cases, the list is prohibitively large, or the files in the list are too large to transfer over the internet.
The question is, How to solve "The certificate is not valid and cannot be used to verify the identity of this website" error? Here are the details: I have a signed applet that has been working fine, until I updated Java to 8u25 (1.8.0_25-b18). I've checked the java console when this happens, and this warning message is displayed right after these lines: security: Obtain certificate collection in SSL Root CA certificate store security: Invalid certificate from HTTPS server network: Cache entry not found [url: https://sub.domain.net:9876, version: null] The application is downloaded from a different domain, say "https://app.domain.net/.....", so no jars are downloaded from "https://sub.domain.net:9876", but the applet connects to "https://sub.domain.net:9876" to send/receive data.