No. CVE-2025-48700
A Synacor Zimbra Collaboration Suite (ZCS) bug is being used in attacks
Being used now
Yes. Attackers are using this right now.
What to do
Apply the vendor's update. If there is none, stop using it or cut it off from the internet.
- Confirmed in attacks
- Apr 20, 2026
- Product
- Synacor Zimbra Collaboration Suite (ZCS)
- Attack likelihood, next 30 days
- 1.7%
Attack likelihood is EPSS, a daily estimate from FIRST.org of how likely this bug is to be used in attacks in the next 30 days.
The official description
Synacor Zimbra Collaboration Suite (ZCS) contains a cross-site scripting vulnerability that could allow attackers to execute arbitrary JavaScript within the user's session, potentially leading to unauthorized access to sensitive information.
For your tech helper
A read-only checklist for whoever helps you with your computer, or an AI assistant. Paste it into Claude, ChatGPT or a coding agent; it only looks and changes nothing.
Read-only check, change nothing, send nothing anywhere.
Is Synacor Zimbra Collaboration Suite (ZCS) (CVE-2025-48700) installed or running on this machine or in this project?
1. Find every copy and its version (apps, packages, containers, lockfiles).
2. Compare each version against the vendor's fixed version for CVE-2025-48700. Quote the vendor page you used.
3. Report a table: where, version, fixed version, status (exposed / fixed / not installed / unsure).
4. List the exact update steps, but do not run them.