Affected: TYPO3 Extension "Apache Solr for TYPO3 - Enterprise Search"

The extension allows a request-provided additionalFilters parameter to register a named siteHash filter before the system's own siteHash filter is applied, and the query builder does not overwrite an already-registered named filter. In a shared Solr core serving multiple TYPO3 sites, a visitor can use this to read public documents belonging to another site. The same root cause also affects the suggest top-results path when suggest is enabled.