Missing check for user PID
When validating a user's email address in the user settings plugin, the user storage page PID is not queried. This distorts the validation result.
$where = 'deleted=0 AND email =\''.mysql_escape_string($email).'\' AND uid <> '.$GLOBALS['TSFE']->fe_user->user['uid'];
must be replaced with
$where = 'deleted=0 AND email =\''.$GLOBALS['TYPO3_DB']->quoteStr($email,'fe_users').'\' AND uid <> '.$this->getUserID().' AND pid = '.$this->getUserProfilePid();
Thanks to Fabian Friedrich for discovering this issue.