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CVE-2026-100821 is a site-isolation vulnerability in Mozilla Firefox's Panning and Zooming component. The issue affects installations that have not received the relevant fixes, which are included in Firefox 157, Firefox ESR 153.4, Firefox ESR 115.42, and Firefox ESR 140.17.
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What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
14 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A network-accessible, low-complexity vulnerability with no required privileges or user interaction, rated with high impacts to confidentiality, integrity, and availability in the provided CVSS v3 vector. The notice identifies Debian Linux 12.0, 13.0, and 14.0, as well as Firefox ESR Debian package CPE data, in its affected CPE information.
A site-isolation vulnerability in Firefox's Panning and Zooming component.
A vulnerability addressed by a Slackware Mozilla Firefox package update; no technical vulnerability details are provided.
A Mozilla Firefox ESR vulnerability referenced by the plugin; no technical details are provided.
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.