Important: #103306 - Frame GET parameter in tx_cms_showpic eID disabled

Description

The show image controller (eID tx_cms_showpic) lacks a cryptographic HMAC-signature on the frame HTTP query parameter (e.g. /index.php?eID=tx_cms_showpic?file=3&...&frame=12345). This allows adversaries to instruct the system to produce an arbitrary number of thumbnail images on the server side.

To prevent uncontrolled resource consumption, the frame HTTP query parameter is now ignored, since it could not be used by core APIs.

The new feature flag security.frontend.allowInsecureFrameOptionInShowImageController — which is disabled per default — can be used to reactivate the previous behavior:

$GLOBALS['TYPO3_CONF_VARS']['SYS']['features']['security.frontend.allowInsecureFrameOptionInShowImageController'] = true;