Philipp. hi, thanks for reporting this. could you go to the firefox menu ≡ > help ? > troubleshooting information page and take a look in the Accessibility section if accessibility is set to "true" there.

if yes, can you please copy & paste this whole section into a reply in the forum and see if the following fixes the performance problem: go to the firefox menu ≡ > options > privacy & security panel and under permissions check the setting to prevent accessibility services from accessing your browser.

Phioipp checking the box to prevent accessibility services from accessing your browser was the answer. Thanks

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