Trying to upgrade a 1.22 version of mediawiki to any of the 1.23 versions will on my shared host result in the following behaviour:
After entering the Upgrade Key and moving on to the "Welcome to MediaWiki"-page, the installer hangs and the page never finishes loading, that is you only see white.
With strategic outcommenting of code, we have narrowed the issue down to the wfShellExec()-Function, however no error was produced. Only when we extracted the offending piece of code where we able to get a warning message.
Test code and warning message: http://slexy.org/view/s2frnrvJCP
Hosteurope's (provider) PHP Version: http://www.hosteurope-infos.de/phpinfo.php
Version: 1.23.3
Severity: normal
URL: https://www.mediawiki.org/wiki/Thread:Project:Support_desk/wfShellExec()_causes_web-installer_(and_possibly_more)_to_hang_in_1.23.3