Microsoft Office 365 Message Encryption Insecure Mode of Operation
Microsoft Office 365 Message Encryption (OME) utilitises Electronic Codebook (ECB) mode of operation. This mode is generally insecure and can leak information about the structure of the messages sent, which can lead to partial or full message disclosure. As stated in the NIST’s "Announcement of Proposal to Revise Special Publication 800-38A": "In the NIST National Vulnerability Database (NVD), the use of ECB to encrypt confidential information constitutes a severe security vulnerability; for example, see CVE-2020-11500.
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