Mitel Alerts Users to Severe XSS Vulnerability in MiContact Center

Mitel has issued a security advisory (MISA-2025-0003) to notify users of its MiContact Center Business software about a high-severity reflected cross-site scripting (XSS) vulnerability.

The vulnerability, identified in its Legacy Chat component, poses significant risks, allowing attackers to execute malicious scripts that could compromise sensitive information.

The flaw, tracked under CVE-2025-23092, carries a CVSS 3.1 base score of 7.1, categorizing it as a “High” severity vulnerability.

Mitel recommends immediate action to mitigate risks by applying updates or hotfixes to affected product versions or by disabling the vulnerable Legacy Chat functionality.

Details of the Vulnerability

The vulnerability stems from inadequate input validation in the Legacy Chat module of MiContact Center Business.

If exploited successfully, an unauthenticated attacker can conduct XSS attacks by injecting arbitrary scripts into user sessions.

This exploitation requires user interaction, such as clicking on a malicious link, but once executed, it may allow attackers to:

• Access sensitive information from users.
• Manipulate the active chat session.

While the vulnerability primarily affects confidentiality and integrity, its impact on availability is minimal. The issue predominantly affects deployments that use the Legacy Chat functionality.

Affected Products

Mitel has identified the following MiContact Center Business versions as vulnerable:

Product Name	Version(s) Affected	Solution(s) Available
MiContact Center Business	10.2.0.0 through 10.2.0.4	Upgrade to version 10.2.0.5 or later.
	10.1.0.0 through 10.1.0.5	Apply hotfix KB571322 or upgrade further.
	10.0.0.0 through 10.0.0.4	Apply hotfix KB571372 or upgrade further.
	9.5.0.3 and earlier	Apply hotfix KB571320 or upgrade further.

Products that have reached their End of Support (EOS) status are not covered under this advisory.

Mitigation and Recommended Actions

Immediate Fixes

Mitel has released specific fixes and hotfixes for the affected versions:

1. Hotfix KB571322: For version 10.1.0.5.
2. Hotfix KB571372: For version 10.0.0.4.
3. Hotfix KB571320: For version 9.5.0.3.

Alternatively, users are advised to upgrade to MiContact Center Business version 10.2.0.5 or later, where this vulnerability has been resolved.

Other Mitigation Measures

• Disable the Legacy Chat feature if it’s not being actively used.
• Transition to the CloudLink Contact Center Messenger Chat, which is not impacted by this issue.
• Follow the mitigation guidelines in Mitel Knowledge Base article SO8420.

The vulnerability’s attack vector is over the network, with low attack complexity. However, it requires user interaction, making it critical for organizations to promptly address the flaw to avoid potential exploitation.

Mitel is urging all affected customers to act quickly by applying the recommended updates and hotfixes to secure their systems.

For deployments relying on Legacy Chat, disabling the feature or migrating to an alternative chat solution is strongly advised. Customers are encouraged to reach out to their Mitel Authorized Partners or Mitel Product Support for assistance.

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