According to [https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#valid-floating-point-number](the HTML spec), a number with a trailing decimal point is not considered valid, and should [fail to parse](https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#rules-for-parsing-floating-point-number-values). This is checked by the [html/semantics/forms/the-input-element/number.html](https://wpt.fyi/results/html/semantics/forms/the-input-element/number.html) web platform test, which Firefox was failing before [bug 1821569](https://bugzilla.mozilla.org/show_bug.cgi?id=1821569) was resolved. That patch did not include the [constraint validation](https://html.spec.whatwg.org/multipage/input.html#number-state-\(type=number\)) that should be setting the bad input flag, so that needs to be fixed at the very least.
Bug 1839572 Comment 8 Edit History
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According to [the HTML spec](https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#valid-floating-point-number), a number with a trailing decimal point is not considered valid, and should [fail to parse](https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#rules-for-parsing-floating-point-number-values). This is checked by the [html/semantics/forms/the-input-element/number.html](https://wpt.fyi/results/html/semantics/forms/the-input-element/number.html) web platform test, which Firefox was failing before [bug 1821569](https://bugzilla.mozilla.org/show_bug.cgi?id=1821569) was resolved. That patch did not include the [constraint validation](https://html.spec.whatwg.org/multipage/input.html#number-state-\(type=number\)) that should be setting the bad input flag, so that needs to be fixed at the very least.