Tor Browser is preventing add-on from saving its setting

TL:DR; I've downloaded an add-on from mozilla, and when I try to configure it the TorButton cleared its settings.

Detail: First, I thought this might be an add-on's bug. I tested the add-on with Mozilla Firefox ESR and Firefox 57. Both worked without problem. So I removed the add-on from Tor browser and tried this[1]. When I clicked "Save", it cleared all forms. The Browser console said TorButton is causing this issue.

I understand you don't want users to add any add-ons to your browser. But isn't this too much?

[1] https://trac.torproject.org/projects/tor/attachment/ticket/24783/samplefortor.zip

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