TYPO3 Core

- Install TYPO3 as a subdomain, e.g., http://www.domain.tld/subdomain
- Map a domain, e.g., http://www.somewhere.com to somewhere in the pagetree
- Activate FE editing with pageTS from http://typo3.org/documentation/tips-tricks/frontend-editing/ without hiding the panel itself

When showing a page corresponding to a page in the somewhere.com subtree with frontend editing, the URL is actually http://www.domain.tld/subdomain/index.php?id=X. The form encapsulating the frontend editing panel as a relative action to /subdomain/index.php and a few parameters. However with RealURL, there is a baseURL in the head section that states that relative URL should be prefixed with http://somewhere.com.

This leads to a "missing postVarSet" error from RealURL.

Solution: generate the form action with an absolute URL instead.

(issue imported from #M9600)