China-Linked Threat Actors Exploit Chrome-Windows Zero-Day Chain to Deploy GRIMWEDGE and SUPERSTOMP

China-linked hackers exploited a zero-day chain in Chrome and Windows to deploy GRIMWEDGE, a backdoor, while another group used the same chain for SUPERSTOMP. The exploit leveraged a patch gap in Chrome, highlighting the risks of delayed updates.

A Chinese threat actor has been attributed to a spear-phishing campaign that exploits recently patched security flaws in Google Chrome and Microsoft Windows to deliver a malicious JavaScript backdoor called GRIMWEDGE.

Volexity, which is tracking the threat cluster under the moniker UTA0560, said the activity targeted multiple non-governmental organizations (NGOs) on September 1, 2026.

"The

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