# BingBang: AAD misconfiguration led to Bing.com results manipulation and account takeover

Multi-tenant AAD apps lacking token claim validation let any Azure user log into Microsoft's Bing Trivia CMS, enabling Bing search result manipulation and XSS that stole Office 365 tokens.

- Payout: $40,000
- Severity: critical
- Program: Microsoft Azure AD
- Credited: Wiz Research
- Disclosed: 2023-03-29
- Write-up quality: 8/10
- Original: https://www.wiz.io/blog/azure-active-directory-bing-misconfiguration
- Library page: https://bugbountylibrary.com/r/blog%3Awiz-io-blog-azure-active-directory-bing-misconfiguration
- Tags: domain:cloud impact:ato impact:data-leak kind:research platform:threat-intel sev:critical tech:azure tech:oauth technique:chained technique:recon vuln:auth-bypass vuln:xss

**Target:** Azure App Services / Azure Functions multi-tenant OAuth apps (bingtrivia.azurewebsites.net CMS)
**Root cause:** Azure App Service authentication only validates token signature, not tenant/issuer claims; multi-tenant apps without app-side authorization checks accept OAuth tokens from any Azure tenant.
**Steps:**
1. Scan Azure App Services/Functions for multi-tenant auth endpoints.
2. Create a user in an attacker-controlled Azure tenant.
3. Obtain an OAuth token for the target app from the attacker tenant and log in to `bingtrivia.azurewebsites.net`.
4. Access CMS sections controlling Bing carousels and homepage content.
5. Edit a carousel entry (e.g. 'best soundtracks' first item) and observe change reflected on Bing.com.
6. Inject XSS payload that calls the Office 365 token endpoint to mint a JWT on behalf of the victim.
7. Exfiltrate token and use it to read Outlook, Teams, SharePoint, OneDrive data.
**How found:** Scanned internet for multi-tenant Azure App Services/Functions, found ~25% vulnerable; focused on Microsoft tenant, spotted bingtrivia.azurewebsites.net, logged in with an external-tenant user, and noticed CMS sections controlling Bing carousels and homepage content.
**Exploitation:** Attacker logs into the exposed CMS with a token from their own tenant, edits Bing search carousel content to inject XSS, and when Bing users view results the payload requests an Office 365 JWT for the victim, exfiltrating it to read the victim's mail, calendar, Teams, SharePoint and OneDrive.
**Escalation:** Chained CMS write access to stored XSS on Bing.com, then leveraged business.bing.com O365 token endpoint to escalate from XSS to full Office 365 data theft across millions of users.
**Insight:** When a cloud IdP offers one-click auth, test whether the app validates issuer/tenant claims by logging in with a token from your own tenant; managed-service auth often checks only signature validity, so multi-tenant apps become auth bypasses.