Important: #95297 - Strict cHash validation feature flag

See forge#95297


Since TYPO3 v9 and the PSR-15 Middleware concept, cHash validation was moved outside of plugins and rendering code inside a validation middleware to check if a given "cHash" acts as a signature of other query parameters in order to use a cached version of a frontend page.

However, the check only provided information about an invalid "cHash" in the query parameters. When no "cHash" was given, the only option was to add a "required list" (global TYPO3 configuration option requireCacheHashPresenceParameters), but not based on the final excludedParameters for cache hash calculation of given query parameters.

For this reason, a new global TYPO3 configuration option $GLOBALS['TYPO3_CONF_VARS']['FE']['cacheHash']['enforceValidation'] has been added.

When enabled, the same validation for calculating a "cHash" value is used as when a valid or invalid "cHash" parameter is given to a request, even when no "cHash" is given.

The new option is disabled for existing installations, but enabled for new installations. It is also highly recommended to enable this option in your existing installations.

In future TYPO3 versions, this functionality will be enabled for all TYPO3 installations, while the configuration option requireCacheHashPresenceParameters will be removed.