An issue was discovered in the Calendar feature in Zimbra Collaboration Suite 8.8.x before 8.8.15 patch 30 (update 1), as exploited in the wild starting in December 2021. An attacker could place HTML containing executable JavaScript inside element attributes. This markup becomes unescaped, causing arbitrary markup to be injected into the document.
Why this VPI (explainable, experimental)
VPI breakdown
| Impact | 61.00 |
| Exploitation signal(KEV listed) | ×1.50 |
| Ransomware bonus | +5.00 |
| VPI | 96.50 |
VPI formula vpi-v1
Required Action
Apply updates per vendor instructions.
| Source | CVSS Version | Base Score | Severity | Vector String | Assessment Date |
|---|---|---|---|---|---|
| NVDNIST | 3.1 | 6.1 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N | 04/20/2026 |
| NVDNIST | 2.0 | 4.3 |
An issue was discovered in the Calendar feature in Zimbra Collaboration Suite 8.8.x before 8.8.15 patch 30 (update 1), as exploited in the wild starting in December 2021. An attacker could place HTML containing executable JavaScript inside element attributes. This markup becomes unescaped, causing arbitrary markup to be injected into the document.
| AV:N/AC:M/Au:N/C:N/I:P/A:N |
| 04/20/2026 |