Again, I apologize for the oversight. You are right, it was a very big oversight. All I can do is apologize and fix the problem. I'm sure there were some people who had problems running mojoPortal 2.6 on old hosting and said nothing. I'm grateful you did let us know and again, I'm sorry we didn't fix the documentation. All of that said, the release notes were extremely clear that this version of mojoPortal must have .NET 4.6.2. The download page at GitHub even shows the requirement.
Regarding the difficulty of upgrading mojoPortal; can you tell me, beyond the problem you have had this time, what makes upgrading mojoPortal so difficult? We're eager to make things better and easier but we need to know what to improve. Your ideas could help.
Regarding "crashing" this site. I do not wish to argue with you but you didn't "crash" the site. You caused an error to be thrown for your user session. The didn't fail for everyone using it, which is what I would consider "crashing" it.
Regarding the error you produced, mojoPortal is a WebForms solution (for now) and as such it uses ViewState. Usually, you would have received a nicer error message but we were in the middle of testing a new feature and had turned off CustomErrors so you got the big, ugly, in-your-face error message. The site doesn't completely "bomb out" without scripts but login does fail. I suspect that login will fail on a great many websites when scripts are disabled. I installed ScriptSafe and was able to browse this site very well. Since you keep referencing WordPress, I decided to check out wordpress.com with ScriptSafe enabled. I could not enter my login credentials at all, which I consider a better experience than getting an error message but it doesn't tell me why I can't enter anything, the form is just disabled. Also, a lot of the site just doesn't load. My point is that when users use tools like ScriptSafe they usually understand that sites aren't going to work 100% bug free. I would never expect any site to work completely when using a tool like ScriptSafe. I also wouldn't be alarmed by sites that give me ugly errors when I have ScriptSafe enabled.
I hope to help you get your site up and running with mojoPortal 2.6 and to make the upgrade process smoother in the future. As for documentation, we could use all of the help we can get. mojoPortal is a big project and it has been around a very long time. There is a lot of documentation that needs to be updated so if you wouldn't mind helping, please let us know.