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CVE-2026-74970 is a site-isolation vulnerability in the Mozilla Graphics component. The flaw weakens the browser's site-isolation security boundary, potentially permitting content from one isolated site context to affect or access resources associated with another context. Mozilla fixed the issue in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository is a small proof-of-concept for CVE-2026-74970, a Firefox/WebRender Fission site isolation bypass caused by missing namespace ownership validation on PipelineId handling. The repo contains three files: a README explaining the vulnerability and reproduction steps, poc.patch containing the Firefox source modifications, and poc.html containing a trigger page. The exploit is not a standalone remote exploit; it is a browser-internal PoC that assumes an already-compromised Firefox content process. The patch alters CompositorBridgeChild::GetNextPipelineId() so that, when running in a content process and when MOZ_POC_FORGE_WR_NAMESPACE is set, the high 32-bit PipelineId namespace is replaced with an attacker-chosen value. A second patch in WebRenderBridgeParent::AddPipelineIdForCompositable() logs when the GPU-side parent accepts a PipelineId whose namespace does not match the sender's namespace. The HTML page uses a WebGL canvas to create an async image pipeline and a cross-origin iframe to exercise Fission/OOP iframe behavior, helping trigger AddPipelineIdForCompositable. Successful exploitation demonstrates cross-origin rendering confusion and cross-tab denial of service by overwriting a victim async image pipeline in the shared AsyncImagePipelineManager. There is no code execution payload, persistence, or external C2; this is a targeted logic-bypass PoC for browser process isolation validation.
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14 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
Site-isolation weakness in Firefox graphics.
A site-isolation flaw in Firefox graphics.
A site isolation issue in Firefox's Graphics component.
Unknown
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.