Open your add-ons manager. Look for anything labeled Legacy. Legacy means that those add-ons will not work in Firefox 57. They will need to be rewritten or replaced.

Please consider turning on send info to Mozilla before posting a question. This helps us help you. If you had had it turned on I would have been able to tell you what extensions would no longer work and/or instead I have nothing. You can go to the Extensions/addon page in Firefox and you may see some marked as Legacy. This will be removed on update if the Developer does not intended to keep their program updated. You can also Click the tiny Gear on right top corner of the Extension/addon page and initiate a update call. Please know that Mozilla/Firefox are not responsible for Extensions and addons. They are made by their own Developer/s and are approved for use with Firefox There is contact/support info on each page that Mozilla supplies to the Developer to distribute their Extensions/addons , https://addons.mozilla.org/en-US/firefox/extensions/ If you are wanting to Help Support for Thunderbird they have their own support site : https://support.mozilla.org/en-US/products/thunderbird as well as their own addon page https://addons.mozilla.org/en-US/thunderbird/ and they are not responsible for Thunderbird Extensions/sddons. Note : Firefox 57 Quantum release date Nov 14th https://www.mozilla.org/en-US/firefox/quantum/ Note : Legacy Extensions will be disabled and or removed. Please let us know if this solved your issue or if need further assistance.