Hi,
Those parameters are not coming from the plugin, it seems like that there is a 3rd party script adding an event handler for the search form, and captures either the submit or the keypress events. When I click the magnifier it looks okay, only affects the keypress.
After a bit of debugging I have found that the issue is caused by this file: wp-content/plugins/cleantalk-spam-protect/js/apbct-public-bundle.min.js
From the directory name the plugin name should be something like Cleantalk Spam Protect or similar. It attaches to the form submission event, and the search can’t execute it’s own event handler.