Error 404: Request parameters could not be validated (&cHash empty)

[biedert]

In a freshly installed TYPO3 instance, I get a 404 thrown if I submit the search form supplied by the "Search form" plugin. The content of the 404 page says: "Request parameters could not be validated (&cHash empty)"

How to replicate: Set up fresh Instance of TYPO3 11.5.27, install the newest version of events2 (currently 8.1.6). Add the static TS of events2 to the root Template. Add a new page below the root page, add an event to it. Add a new Plugin called "Search form" to the root page and reference the page with the event in the field "Record Storage Page". In the Frontend, submit the search form.