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CVE-2025-27915 is a stored cross-site scripting vulnerability in Zimbra Collaboration Suite affecting ZCS 9.0, 10.0, and 10.1. The flaw resides in the Classic Web Client’s handling of iCalendar (ICS) content, where insufficient sanitization of attacker-controlled HTML embedded in an ICS entry allows script execution when the message is viewed. Reported exploitation uses a JavaScript payload triggered through an ontoggle event associated with a details element rendered from the malicious calendar content. Because the script executes in the context of the victim’s authenticated webmail session, an attacker can interact with mailbox functionality as the user, including manipulating settings and accessing mailbox data.
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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.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
69 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Zimbra vulnerability cited as one of several webmail flaws targeted by TA458 in its espionage operations.
A zero-day cross-site scripting vulnerability in Zimbra webmail servers exploited by TA458 as part of its webmail-focused espionage operations.
A previously exploited vulnerability affecting Zimbra Collaboration Suite, mentioned as historical context for similar flaws.
A stored XSS flaw in Zimbra Classic Web Client that was alleged to have been exploited as a zero-day against the Brazilian military, though Zimbra said it found no evidence supporting that claim.
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.