TYPO3 Core

problem:
if an alternative TYPO3-logo is set in $GLOBALS['TBE_STYLES']['logo'] and a skin-extension is installed in 'typo3/ext/' (globally), the file 'typo3/backend.php' does not check the image-dimensions. instead it outputs the alternative image with the size of the default logo.

solution:
just remove the substring-check '../', resolve the backpath to the alternative logo-file and always run through 'getimagesize'.

and i am sorry, i dont know where this function is actually used (maybe it is deprecated?), so i dont know how to test it, because the logo-image on the upper left is processed by 'typo3/classes/class.typo3logo.php'.
...BUT: the file 'typo3/backend.php' just contains the same issue as reported in http://bugs.typo3.org/view.php?id=13985

(issue imported from #M13988)