I just executed the upgrade to wb2.8rc1 successfully and have 2 recommodations for the Upgrade documentation on page http://start.websitebaker2.org/de/wb-2.8.php
(and according to the English help page):
1. Paragraph "Prerequisites", Step 6. ("News Modul / Form Modul")
This para ought to be moved to the section "Backup" (above from "Prerequisites").
When one followed step 1 to 5 within "Prerequisites", one is no longer able to execute para 6. in "Prerequisites", because one is no longer able to access the backend for copying the "News-Modul" options i.e. to a plain text file. So this step ought to be a part of the section "Backup".
2. The following para is missing in the Upgrade manual:
"If you renamed folders within your WB 2.7 core installation (i.e. "admin" to "master" and/or "media" to "multimedia" or something like that), you must rename the same folders within your WB 2.8 RC1 directories *before* uploading these files to your server. Otherwise the upgrade will fail, because these changed folder names are set in the config.php and in the options of the backend".
Have a nice day