Regarding the current default certificate issue: What is the easiest/fastest solution?

First: Please have a closer look at our certificate issue article in SIOS.

While the default certicates must not be used in productive environements the replacement of them may act as a fast, intermediate solution until you have created and rolled out your own certificates.

1. Download the default certificates of the newer versions of WinCC OA here.
   They have a much longer expiration date than the ones that were present in the WinCC OA Version 3.12 to 3.16.
   But eventually even those will expire in 2050 too, so please take your time to create your own certificates AND establish a process of replacement for those as well.
2. Extract the files from the archive.
3. Search for the respective files in your project directory and just replace the files with the ones from the archive.
4. Restart your project afterwards to put the new certificates in effect.