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.

Thank you for your response. The Accessibility is marked True. I will try your suggestion.