Without having yet done more detail, I'd say by eyeball my informed guess is that the issue is [here](https://searchfox.org/mozilla-central/rev/0e93b94f4c2045c6a5f5260ee48bbf7a94a993bc/dom/streams/ReadableStreamPipeTo.cpp#698,700,709), where we attempt to process a JSException by calling into JSAPI while that exception is still pending on the JSContext We need to instead ensure the exception has been removed from the JSContext before doing error handling.
Bug 1764117 Comment 2 Edit History
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Without having yet done my own reproduction, I'd say by eyeball my informed guess is that the issue is [here](https://searchfox.org/mozilla-central/rev/0e93b94f4c2045c6a5f5260ee48bbf7a94a993bc/dom/streams/ReadableStreamPipeTo.cpp#698,700,709), where we attempt to process a JSException by calling into JSAPI while that exception is still pending on the JSContext We need to instead ensure the exception has been removed from the JSContext before doing error handling.