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CVE-2025-66376 is a stored cross-site scripting vulnerability affecting the Classic UI of Zimbra Collaboration 10.0 before 10.0.18 and 10.1 before 10.1.13. The client-side HTML sanitizer inadequately handles CSS @import directives in crafted HTML emails. Attackers can fragment executable markup with fake @import directives and HTML comments so that sanitization allows the browser to reconstruct and execute malicious JavaScript. Opening or previewing the message triggers execution within the recipient’s authenticated webmail session, without a link click or attachment opening. The vulnerability was exploited as a zero-day in espionage campaigns deploying ZimReaper.
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No public exploit code observed for this vulnerability.
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157 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A zero-day cross-site scripting vulnerability in Zimbra Collaboration Suite that enabled a zero-click email attack: malicious HTML embedded in an email could execute when a recipient opened or previewed it, enabling compromise of the webmail server and access to mailboxes and authentication data.
A vulnerability in certain Zimbra Collaboration Suite versions that can allow execution of malicious code when a user views a malicious email made to appear legitimate. Successful exploitation risks email and sensitive-data theft, unauthorized account access, and subsequent abuse of compromised accounts.
A Zimbra Collaboration Suite webmail vulnerability reportedly exploited through crafted emails in a zero-click phishing campaign, enabling compromise when a recipient views the email and allowing theft of email correspondence, session tokens, and credentials.
A vulnerability in Zimbra Collaboration Suite used in a zero-click or 'half-click' email espionage campaign, where viewing a crafted message in vulnerable Zimbra webmail was enough to trigger exploitation and enable theft of email, session tokens, and credentials.
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Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.