mozregression says it's a regression from Bug 1575095. I'm pretty sure my specific issue is not that old but Twitter might did some change on their side.
Bug 1665942 Comment 1 Edit History
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mozregression says it's a regression from Bug 1575095, specifically https://phabricator.services.mozilla.com/D76841. I'm pretty sure my specific issue is not that old but Twitter might did some change on their side.