I have unzipped a Firefox extension and made some minor modifications in the source code. When I read the instructions for signing extensions here https://extensionworkshop.com/documentation/publish/signing-and-distribution-overview/ it seems that I have to use Mozilla's signing mechanism, even though I only intend to use this modified extension myself.
Submitting a modified version of an existing extension seems problematic from a copyright point of view, even though just using it privately should cause no legal problems, shouldn't it? How do I get around this situation?