In 2024 and 2025, cybersecurity researchers disclosed four critical vulnerabilities in Microsoft Teams that collectively enable attackers to impersonate colleagues, manipulate message content, and forge notifications without leaving typical indicators such as 'Edited' labels. These flaws allow an attacker to alter the sender's displayed identity in messages and call notifications, effectively bypassing built-in trust mechanisms. The vulnerabilities affect both internal users and external guests, broadening the attack surface. Attackers can exploit these weaknesses to conduct sophisticated social engineering campaigns, such as sending malicious links or requests appearing to come from trusted executives or colleagues, increasing the likelihood of successful phishing or data exfiltration. One notable vulnerability, CVE-2024-38197, scored 6.5 CVSS and impacts Teams on iOS, allowing sender name spoofing. Microsoft released patches starting August 2024, with further updates through October 2025. The flaws highlight a shift in attack strategies from breaching systems to undermining trust in communication platforms, which are now as critical as email for business operations. The vulnerabilities also allow modification of conversation topics and display names in calls, enabling forged caller identities. This erosion of trust in collaboration tools can facilitate unauthorized access, data leaks, and operational disruption, especially as Teams is widely adopted globally, including across Europe. The threat is compounded by the platform's extensive use for messaging, calls, meetings, and screen sharing, all weaponized at various attack stages. Organizations must recognize that attackers exploit perceived trust rather than technical breaches, necessitating new security paradigms focused on verification and user awareness.

European organizations face significant risks from these Microsoft Teams vulnerabilities due to the platform's widespread adoption in corporate, governmental, and educational sectors across Europe. The ability to impersonate trusted colleagues and executives can lead to successful spear-phishing attacks, resulting in credential theft, unauthorized access to sensitive data, financial fraud, and intellectual property loss. Manipulation of message content and notifications undermines communication integrity, potentially causing operational disruptions and damaging organizational reputation. The threat extends to both internal and external collaboration scenarios, increasing exposure in multinational and cross-border projects common in Europe. Given the reliance on Teams for critical business functions, exploitation could also facilitate lateral movement within networks, enabling further compromise. The social engineering aspect is particularly dangerous in environments with less mature security awareness or where verification processes are weak. Additionally, the ability to forge caller identities in calls can be exploited for fraudulent transactions or to bypass voice-based authentication mechanisms. Overall, these vulnerabilities pose a medium to high risk to confidentiality, integrity, and availability of communications and data within European enterprises.

1. Ensure all Microsoft Teams clients and related infrastructure are updated with the latest patches released between August 2024 and October 2025, including fixes for CVE-2024-38197. 2. Implement strict multi-factor authentication (MFA) across all user accounts to reduce the risk of account compromise. 3. Enhance user training focused on recognizing social engineering tactics, emphasizing verification of unexpected or unusual messages, especially those requesting sensitive information or actions. 4. Deploy advanced email and messaging security solutions capable of detecting and flagging anomalous message patterns or spoofing attempts within Teams communications. 5. Establish clear organizational policies requiring out-of-band verification (e.g., phone call confirmation) for sensitive requests, particularly those involving financial transactions or data sharing. 6. Monitor Teams logs and communication metadata for unusual activities, such as unexpected changes in message content or sender identities. 7. Limit guest user permissions and enforce strict access controls to minimize exposure from external collaborators. 8. Consider deploying endpoint detection and response (EDR) tools with capabilities to detect lateral movement and suspicious behavior originating from compromised Teams accounts. 9. Collaborate with Microsoft support and security teams to stay informed about emerging threats and additional patches or mitigations. 10. Integrate Teams security posture into broader enterprise risk management and incident response plans, ensuring rapid containment and remediation if exploitation is suspected.