Office 365 is Microsoft's cloud productivity suite, whose identity, email, and data controls make its vulnerabilities and security advisories consequential.
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Background for this topic.
Office 365 is Microsoft’s cloud-hosted productivity and collaboration service, encompassing Exchange Online email, SharePoint, OneDrive, Teams, and web and desktop Office applications. Because these services store communications and business documents in a shared cloud environment, the tag includes both attacks against the platform and security issues arising from tenant configuration, identity, and connected applications.
Material risks include phishing or stolen credentials leading to account takeover, malicious OAuth applications gaining delegated access, mailbox forwarding rules, and excessive external sharing of files. Effective defenses include phishing-resistant multifactor authentication, conditional-access policies, least-privilege administration, controlled app consent, data-loss prevention, and review of audit and sign-in logs. Security teams must also track Microsoft advisories and client vulnerabilities, preserve cloud evidence for investigations, and apply retention, privacy, and compliance controls appropriate to the data stored in the tenant.
Weekly headline count for the current query.
Microsoft is working to address a widespread service issue affecting the mail flow pipeline for Exchange Online customers across North America and Germany. [...]
Microsoft says it will start blocking legacy TLS connections for POP and IMAP email clients in Exchange Online starting in July 2026. [...]
Microsoft is investigating and working to resolve Exchange Online mailbox access issues that have intermittently affected Outlook mobile and macOS users for weeks. [...]
Microsoft is working to address an ongoing service issue that has intermittently prevented some users from accessing their cloud-based Exchange Online mailboxes via Outlook mobile and Mac desktop clients since Thursday. [...]
Microsoft is working to address an ongoing Exchange Online outage that is preventing customers from accessing their mailboxes and calendars. [...]
Microsoft says an Exchange Online issue that mistakenly quarantined legitimate emails last week was triggered by faulty heuristic detection rules designed to block credential phishing campaigns. [...]
Microsoft is investigating an ongoing Exchange Online issue that mistakenly flags legitimate emails as phishing and quarantines them. [...]
Microsoft announced today that the Exchange Web Services (EWS) API for Exchange Online will be shut down in April 2027, after nearly 20 years. [...]
Microsoft is working to fix an Exchange Online service outage that intermittently prevents users from accessing their mailboxes via the Internet Mailbox Access Protocol 4 (IMAP4). [...]
Microsoft announced today that it has canceled plans to impose a daily limit of 2,000 external recipients on Exchange Online bulk email senders. [...]
Microsoft announced on Monday that it will soon block mobile devices running outdated email software from accessing Exchange Online services until they're updated. [...]
Microsoft is investigating an Exchange Online service outage that is preventing customers from accessing their mailboxes using the classic Outlook desktop client. [...]
Microsoft has reminded that Exchange Server 2016 and 2019 reached the end of support and advised IT administrators to upgrade servers to Exchange Server SE or migrate to Exchange Online. [...]
Microsoft is working to resolve an ongoing outage preventing users from accessing Microsoft 365 services, including Microsoft Teams, Exchange Online, and the admin center. [...]
Microsoft is enabling threshold-based auto-archiving by default in Exchange Online to prevent email flow issues caused by mailboxes filling up faster than expected. [...]
Microsoft is investigating a known issue that causes the classic Outlook email client to crash upon launch, which can only be resolved via Exchange Online support. [...]
Microsoft is working to resolve an ongoing Exchange Online outage affecting customers throughout North America, blocking their access to emails. [...]
Microsoft is working to resolve a known issue that causes an anti-spam service to mistakenly block Exchange Online and Microsoft Teams users from opening URLs and quarantine some of their emails. [...]
Microsoft is working to resolve an Exchange Online issue causing email access problems for Outlook mobile users who use Hybrid Modern Authentication (HMA). [...]
Microsoft has warned customers to mitigate a high-severity vulnerability in Exchange Server hybrid deployments that could allow attackers to escalate their privileges in Exchange Online cloud environments without leaving any traces. [...]