TYPO3 Core

If you want to save a users session in an eID script you would call
tslib_feUserAuth::storeSessionData()

to save the data to the session table.

From v4.5.22 to 4.5.23 there appears a new condition in this method:
} elseif ($this->sessionDataTimestamp === NULL) {

but $this->sessionDataTimestamp is defind this way:
protected $sessionDataTimestamp;
and will never be filled (therefore will never be NULL)

And for the "elseif" there is NO "else"-branch. So no error-handling at all, just not working.

Note: in 4.7 there IS a "else"-branch (but have not tested 4.7)