Full Report
Cybersecurity researchers have discovered a security flaw in Microsoft's OneDrive File Picker that, if successfully exploited, could allow websites to access a user's entire cloud storage content, as opposed to just the files selected for upload via the tool. "This stems from overly broad OAuth scopes and misleading consent screens that fail to clearly explain the extent of access being granted,
Analysis Summary
# Vulnerability: OneDrive File Picker Over-Permissioning Flaw
## CVE Details
- CVE ID: Not specified in the provided text.
- CVSS Score: Not specified in the provided text.
- CWE: Missing (Implied: Improper Authorization/IDOR due to scope mismanagement).
## Affected Systems
- Products: Microsoft OneDrive File Picker, used in third-party applications integrated with OneDrive via OAuth (e.g., ChatGPT, Slack, Trello, ClickUp).
- Versions: Not specified, implied to affect current versions utilizing the described OAuth flow.
- Configurations: Any application using the OneDrive File Picker for file uploads via OAuth authorization flow that lacks fine-grained scope control.
## Vulnerability Description
The vulnerability stems from the OneDrive File Picker requesting overly broad OAuth scopes, specifically read access to the *entire* OneDrive cloud storage, even when the user intends to only upload a single, specific file. The user consent screen is vague and fails to clearly inform the user about the extent of access being granted (full drive read access). This is compounded by the lack of fine-grained OAuth scopes, preventing users from granting limited access. Furthermore, the resulting OAuth tokens are often stored insecurely in plaintext format within the browser's session storage, and refresh tokens may be issued, granting long-term, persistent access without re-authentication.
## Exploitation
- Status: Not explicitly stated as exploited in the wild, but researchers have demonstrated the flaw.
- Complexity: Low (Given vague consent screens and insecure token storage).
- Attack Vector: Network (Requires user interaction to grant initial authorization).
## Impact
- Confidentiality: High (Potential access to all user files in OneDrive).
- Integrity: Low to Medium (Potential to modify or delete data depending on the full set of granted scopes, though the description focuses on read access).
- Availability: Low to Medium (Potential disruption through excessive reads or token management issues).
## Remediation
### Patches
- Microsoft has acknowledged the issue, but *no fix (patch) is currently available* according to the source.
### Workarounds
1. **Temporary removal:** Temporarily remove the option to upload files using OneDrive via OAuth until a secure alternative is available.
2. **Token Management:** Avoid using refresh tokens if possible.
3. **Secure Storage:** Store access tokens in a secure manner (not plaintext session storage) and ensure they are revoked/deleted when no longer needed.
## Detection
- Indicators of Compromise: Unexpected large data transfers originating from integrated applications, or applications functioning beyond their initially implied scope (e.g., an image editor accessing user documents).
- Detection methods and tools: Monitoring OAuth authorization requests for overly broad scopes being requested against the Microsoft Graph API (specifically OneDrive access) when the corresponding application functionality does not warrant it. Monitoring for plaintext storage of OAuth tokens in application session data.
## References
- Vendor Advisories: Microsoft has acknowledged the report from Oasis Research Team.
- Relevant links:
- news.thehackernews.com/2025/05/microsoft-onedrive-file-picker-flaw.html