https://localhost:8080 uses the obsolete md5 hash in it’s https certificate, if that is your certificate, please (re)create certificate with better algorithm as soon as possible.
What’s running on port 8080? You’ll need to regenerate the certificate to clear that error (as long as new certs aren’t also MD5), you may want to check with the author of whatever app is running on that port on how to generate a more secure certificate, if it’s syno’s cert you can do that in the the GUI I believe (not sure where offhand).