Top 10 Microsoft 365 Security Misconfigurations Found During Assessments
Talk to usMicrosoft 365 security misconfigurations usually fall into two groups: identity and access flaws, and collaboration and sharing risks. The common Microsoft 365 misconfigurations include unenforced MFA, Basic authentication exceptions, too many Global Administrators and permissive external sharing. Each turns a legitimate feature into an attack path. Microsoft protects the underlying service, but organizations remain directly responsible for securing their tenant settings and permissions.
What Is a Microsoft 365 Security Misconfiguration?
A Microsoft 365 security misconfiguration is an insecure default, incomplete control, or setting that nobody revisited. It is not a software bug or CVE. Microsoft secures the cloud platform, while the customer controls tenant identities, permissions and sharing under the shared-responsibility model.
One control appears repeatedly throughout these assessments is:
Conditional Access:
Microsoft Entra’s if/then rule engine for allowing, challenging or blocking sign-ins according to risk, location and device status.
Identity and Access Flaws
Identity and access misconfigurations in Microsoft 365 pertain to errors related who can enter the tenant and what they can reach after signing in.
Unenforced or Weak Multi-Factor Authentication (MFA)
An MFA misconfiguration exposes password-only or SMS-reliant accounts to phishing and credential stuffing. An official Microsoft study measured 99.22% lower compromise risk with multi-factor authentication.
Phishing-resistant MFA: Passkeys, security keys, Windows Hello or certificates. SMS does not qualify.
Legacy Authentication Protocols Left Enabled
The critical legacy authentication risk in Microsoft 365 is Basic authentication, once common with IMAP, POP3 and SMTP AUTH. Remaining exceptions can allow password-only access. Users can block them with Conditional Access or Security Defaults.
Excessive Global Admin Accounts
Excess Global Admins multiply the damage from one compromised account. Assign narrower roles and use Privileged Identity Management for privileges that activate only when required, then expire.
Missing or Incomplete Conditional Access Policies
A Conditional Access misconfiguration can make a stolen password usable from any device or location. A baseline policy should evaluate:
- Device compliance
- Network or location risk
- User and sign-in risk
Also read: 8 IAM Challenges Every Organization Faces
Collaboration and Sharing Risks
Identity and access misconfigurations in Microsoft 365 pertain to errors related who can enter the tenant and what they can reach after signing in.
Permissive External Sharing in SharePoint and OneDrive
Poorly governed external sharing in SharePoint and OneDrive can expose sensitive files without oversight. Match each sharing tier to the data:
| SHARING TIER | EXPOSURE |
| Anyone with the link | No sign-in; access cannot be attributed |
| New and existing guests | External access after authentication |
| Only people in your organization | Internal access only |
Unrestricted Third-Party App Consent (OAuth Risk)
Unrestricted third-party app consent can grant malicious apps mailbox or file permissions. Require an administrator approval workflow for new requests.
OAuth app:
A third-party application authorised to access Microsoft 365 data without receiving the user’s password
Disabled or Under-Retained Audit Logging
Unified Audit Logs in Microsoft 365 are enabled by default for most tenants, with 180-day standard retention. Assessors still verify workload coverage, licensing and retention because missing events can make a breach impossible to reconstruct or report.
Email, Data, and Governance Gaps Assessors Also Flag
These Microsoft 365 misconfiguration assessment findings fall outside the two main categories but surface just as regularly in real tenants.
Unmonitored Mail Forwarding Rules and Malicious Inbox Rules
Inbox rule abuse in Microsoft 365 often follows mailbox compromise. Attackers silently forward messages or delete incoming warnings. Block external auto-forwarding by default, document exceptions and audit rule changes regularly.
Inactive or Orphaned User Accounts with Standing Access
Inactive user accounts in Microsoft 365 quietly expand the attack surface. Disable former employee, contractor and test accounts promptly, recover unused licenses and run quarterly access reviews.
Ignoring Microsoft Secure Score and Skipping Periodic Reviews
Tenants drift as people, licenses and features change. A practical M365 security review cadence checks Microsoft Secure Score, recommendations and Conditional Access quarterly.
Microsoft Secure Score supports prioritization. It does not prove that organisation-specific risks are controlled.
How These Misconfigurations Are Typically Found During a Security Assessment
The Microsoft 365 security assessment process combines automated checks with manual judgement:
- Scan configurations against recognized benchmarks.
- Inspect Conditional Access and privileged roles.
- Audit sharing and application consent.
- Verify audit retention and Secure Score.
- Rank risks and assign owners and deadlines.
How to Prioritize and Fix Microsoft 365 Misconfigurations
Use this impact-led Microsoft 365 security checklist as a starting order:
- Enforce phishing-resistant MFA for administrators.
- Block legacy authentication.
- Reduce permanent Global Administrators.
- Tighten external sharing.
- Restrict application consent.
- Verify audit retention.
- Review Secure Score quarterly.
The checklist supports triage, not a full assessment.
Why Run a Professional Microsoft 365 Security Assessment with Paramount Assure
Paramount combines managed security, GRC and cloud expertise to benchmark tenants against CIS and Microsoft frameworks. Our Microsoft 365 security assessment converts findings into a prioritized remediation roadmap with owners.
