IMHO, this is certainly FF. FF 70a1 Works: 20190723155748 Broken: 20190724095428 . Firefox Setup 69.0b9.exe is also broken. (That was the latest available at the time when I downloaded to check Beta.) (FF 69, nightly, at least up to the time to switchover to FF 70, nightly, was OK. All earlier "Mozilla" were fine.) I'll note that while the bookmarklet worked in earlier Quantum, it only became feasible - for me, once this landed: Bug 1478037 Allow bookmarklets to run even when the CSP on the page would normally block javascript: execution
Bug 1570845 Comment 3 Edit History
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IMHO, this is certainly FF. FF 70a1 Works: 20190723155748 Broken: 20190724095428 . Firefox Setup 69.0b9.exe is also broken. (That was the latest available at the time when I downloaded to check Beta.) (FF 69, nightly, at least up to the time to switchover to FF 70, nightly, was OK. All earlier "Mozilla" were fine.) I'll note that while the bookmarklet worked in earlier Quantum, it only became feasible - for me, once this landed: Bug 1478037 Allow bookmarklets to run even when the CSP on the page would normally block javascript: execution So maybe it's something on the security end, a "clearclick"-like "enhancement"? (There are a couple security bugs during that period that are not public yet.)