Weaponized Microsoft Outlook Add-ins Exploit User Credentials

Gbhackers

Weaponized Microsoft Outlook Add-ins Exploit User Credentials

First seen 12 Feb 2026, 12:40 UTC • •39.7

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ThreatCluster •March 12, 2026 at 16:10 UTC

A dormant Microsoft Outlook add-in has been weaponized, leading to the theft of thousands of login credentials and credit card numbers. This incident marks the first known malicious Office add-in discovered in the wild, revealing a critical flaw in Microsoft's distribution of third-party tools. Additionally, a new attack technique called 'Exfil Out&Look' has been identified, allowing threat actors to exfiltrate sensitive email data without leaving forensic traces.

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Updated 228d ago How this analysis works

Timeline

2022-01-01

Developer published the dormant Outlook add-in

2026-01-29

Exfil Out&Look attack technique reported

2026-02-12

Microsoft Outlook add-in weaponization reported

More articles in this cluster (9)

Threat Graph

15 entities, 27 inferred relationships (STIX 2.1).

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Technique (8)

Data Breach
Malware
Phishing
T1003 - OS Credential Dumping
T1041 - Exfiltration Over C2 Channel
T1071 - Application Layer Protocol
T1566.002 - Spearphishing Link
T1566 - Phishing

Organization (3)

Microsoft
Outlook
Vercel

Malware (1)

AgreeTo

Affected Platform (3)

Microsoft 365
Microsoft Office
Microsoft Outlook

Relationships

AgreeTo targets Microsoft
AgreeTo targets Outlook
AgreeTo targets Vercel
Data Breach targets Microsoft 365
Data Breach targets Microsoft Office
Data Breach targets Microsoft Outlook
Malware targets Microsoft 365
Malware targets Microsoft Office
Malware targets Microsoft Outlook
Phishing targets Microsoft 365
Phishing targets Microsoft Office
Phishing targets Microsoft Outlook
T1003 - OS Credential Dumping targets Microsoft 365
T1003 - OS Credential Dumping targets Microsoft Office
T1003 - OS Credential Dumping targets Microsoft Outlook
T1041 - Exfiltration Over C2 Channel targets Microsoft 365
T1041 - Exfiltration Over C2 Channel targets Microsoft Office
T1041 - Exfiltration Over C2 Channel targets Microsoft Outlook
T1071 - Application Layer Protocol targets Microsoft 365
T1071 - Application Layer Protocol targets Microsoft Office
T1071 - Application Layer Protocol targets Microsoft Outlook
T1566.002 - Spearphishing Link targets Microsoft 365
T1566.002 - Spearphishing Link targets Microsoft Office
T1566.002 - Spearphishing Link targets Microsoft Outlook
T1566 - Phishing targets Microsoft 365
T1566 - Phishing targets Microsoft Office
T1566 - Phishing targets Microsoft Outlook

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