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Page generated: 11 Nov 2026, 13:37 UTC
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CVE-2025-27915

An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0 and 10.1. A stored cross-site scripting (XSS) vulnerability exists in the Classic Web Client due to insufficient sanitization of HTML content in ICS files. When a user views an e-mail message containing a maliciou…

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An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0 and 10.1. A stored cross-site scripting (XSS) vulnerability exists in the Classic Web Client due to insufficient sanitization of HTML content in ICS files. When a user views an e-mail message containing a malicious ICS entry, its embedded JavaScript executes via an ontoggle event inside a <details> tag. This allows an attacker to run arbitrary JavaScript within the victim's session, potentially leading to unauthorized actions such as setting e-mail filters to redirect messages to an attacker-controlled address. As a result, an attacker can perform unauthorized actions on the victim's account, including e-mail redirection and data exfiltration.
CVSS 5.4 (MEDIUM) KEV: KNOWN CATALOG

Attention and evidence

HYPE SCORE
0.0/10
REALITY · THREAT PRIORITY
7.8/10
General review priority; not probability

Evidence confidence: Exploitation recorded

Why this priority?
  • Recorded exploitation baseline: +7.00
  • Technical severity: CVSS 5.4: +0.81
  • Fresh EPSS: 4.06%: +0.02

General review priority, not probability, victim count or asset-specific risk. A range covers missing CVSS/EPSS inputs within the current evidence state.

Sources: 10 documents and public datasets.

Hype components

Headline sample (25%)
0/100
Press, 30 days (60%)
0/100
Grounded branding (15%)
0/100
HYPE TOTAL0/100

Sources and documents

Proofpoint
Press · 23 Jul 2026, 07:00 · Operation RoundPress Rolls on with More Half-Click Webmail Zero-Days from TA458 - Proofpoint
The Hacker News
Press · 11 Jul 2026, 07:00 · Critical Zimbra Flaw Could Let Crafted Emails Run Malicious Code in User Sessions - The Hacker News
CyberSecurityNews
Press · 11 Nov 2025, 08:00 · Hackers Weaponizing Calendar Files as New Attack Vector Bypassing Traditional Email Defenses - CyberSecurityNews
The Hacker News
Press · 09 Oct 2025, 07:00 · From Phishing to Malware: AI Becomes Russia's New Cyber Weapon in War on Ukraine - The Hacker News
Security Affairs
Press · 06 Oct 2025, 07:00 · Zimbra users targeted in zero-day exploit using iCalendar attachments - Security Affairs
See all 10 source documents
The Hacker News
Press · 06 Oct 2025, 07:00 · Zimbra Zero-Day Exploited to Target Brazilian Military via Malicious ICS Files - The Hacker News
Dark Reading
Press · 06 Oct 2025, 07:00 · Attackers Exploit Zimbra Zero-Day Via ICS - Dark Reading
Hong Kong Computer Emergency Response Team Coordination Centre
Press · 06 Oct 2025, 07:00 · Zimbra Collaboration Suite Cross-Site Scripting Vulnerability - Hong Kong Computer Emergency Response Team Coordination Centre
CyberSecurityNews
Press · 06 Oct 2025, 07:00 · Hackers Exploit Zimbra Vulnerability as 0-Day with Weaponized iCalendar Files - CyberSecurityNews
BleepingComputer
Press · 05 Oct 2025, 07:00 · Hackers exploited Zimbra flaw as zero-day using iCalendar files - BleepingComputer

Score evolution

● Hype   ● Reality

Earlier evidence-support scores are retained in history; this chart shows only the current priority definition.

First record: hype 0.0 · reality 7.8 (2026-11-02 15:13). The curve appears once the score changes.

Public exploit evidence

0

Public exploit entries / repo candidates

Evidence context and dated references

Reality is general threat/review priority, combining observed exploitation, CVSS severity and fresh EPSS. Evidence confidence is separate. This is not calibrated risk, a victim count or an asset-specific assessment. A range reflects missing numeric inputs.

Evidence in context

Confidence in exploitation evidence
Exploitation recorded
Priority basis
Recorded exploitation; CVSS 5.4; EPSS 4.1%
Attention, last 30 days
0 distinct story titles; 0 press documents; 0 publisher domains.
Technical potential
network access, low privileges, user interaction.
Observed activity
Exploitation recorded in CISA KEV.
Known scale
Not quantified.
Evidence confidence basis
Trusted exploitation confirmation

Score evaluated: 2026-11-05 13:59:32.825259+00:00 · EPSS snapshot: 2026-11-05T12:03:04Z

Source event timeline
Published
12 Mar 2025, 00:00
First press mention
05 Oct 2025, 07:00
Added to the CISA KEV catalog
07 Oct 2025, 00:00
Latest press mention
23 Jul 2026, 07:00
Score calculated
05 Nov 2026, 13:59
Source: CVE List V5 · CISA KEV · FIRST EPSS · GitHub · RSSVulnRadar