Budibase: SSO OAuth2 Token Leakage via User Metadata Endpoints to Power-Role Users

Summary

The /api/users/metadata and /api/users/metadata/:id endpoints in @budibase/server return full global user profiles to any user with POWER role or above. For SSO-authenticated users (OIDC, Google), the response includes oauth2.accessToken and oauth2.refreshToken fields, leaking identity provider credentials to other users who should not have access to them.

Details

When a user authenticates via SSO (OIDC or Google), the OAuth2 tokens are stored in the global CouchDB user document at packages/backend-core/src/auth/auth.ts:170-173:

dbUser.oauth2 = {
  ...dbUser.oauth2,
  ...details,
}
await db.put(dbUser)

The user metadata endpoints are protected by PermissionType.USER, PermissionLevel.READ (packages/server/src/api/routes/user.ts:11), which maps to the POWER permission set (packages/backend-core/src/security/permissions.ts:99).

Path 1 — List all users (GET /api/users/metadata): 1. controller.fetchMetadata → sdk.users.fetchMetadata() (packages/server/src/sdk/users/utils.ts:78) 2. → getGlobalUsers() → getRawGlobalUsers() (packages/server/src/utilities/global.ts:101-122) — strips only password and forceResetPassword 3. → processUser() (packages/server/src/utilities/global.ts:15-76) — strips only password and roles 4. The oauth2 field containing accessToken and refreshToken is never removed

Path 2 — Single user (GET /api/users/metadata/:id): 1. controller.findMetadata → getFullUser() (packages/server/src/utilities/users.ts:6) 2. → getGlobalUser() → getRawGlobalUser() (packages/server/src/utilities/global.ts:90-92) — raw CouchDB fetch, no field stripping at all 3. → processUser() — strips only password and roles 4. Same result: oauth2 tokens are returned

There is no output sanitization middleware on these routes that would strip sensitive fields before the response reaches the client.

PoC

Prerequisites: A Budibase instance with at least one SSO-authenticated user (OIDC or Google) and a separate user with POWER role in an app.

Step 1 — As the POWER user, list all users: ``bash curl -s -X GET 'http://localhost:10000/api/users/metadata' \ -H 'Cookie: budibase:auth=' \ -H 'x-budibase-app-id: app_' | jq '.[].oauth2' ``

Expected output: null for all users (tokens should not be exposed)

Actual output: For SSO users, the response includes: ``json { "accessToken": "ya29.a0ARrdaM...", "refreshToken": "1//0eXxXxXxXx..." } ``

Step 2 — Fetch a specific SSO user's profile: ``bash curl -s -X GET 'http://localhost:10000/api/users/metadata/ro_ta_users_us_' \ -H 'Cookie: budibase:auth=' \ -H 'x-budibase-app-id: app_' | jq '.oauth2' ``

This also returns the full OAuth2 tokens.

Impact

• A user with POWER role in any app can read all SSO users' OAuth2 access tokens and refresh tokens via the list endpoint, without needing to know individual user IDs.
• Stolen access tokens can be used to access external identity provider resources (Google Workspace, Azure AD, Okta-protected services) as the victim user.
• Refresh tokens allow indefinite token renewal, persisting access even after the original access token expires.
• Additionally, admin, builder, tenantId, ssoId, and userGroups fields are leaked, revealing the full authorization topology of the instance.

Recommended

Fix

Strip sensitive SSO fields in processUser() at packages/server/src/utilities/global.ts:15:

export async function processUser(
  user: ContextUser,
  opts: { appId?: string; groups?: UserGroup[] } = {}
) {
  if (!user || (!user.roles && !user.userGroups)) {
    return user
  }
  user = cloneDeep(user)
  delete user.password
+ delete (user as any).oauth2
+ delete (user as any).provider
+ delete (user as any).providerType
+ delete (user as any).thirdPartyProfile
+ delete (user as any).profile
+ delete (user as any).ssoId
+ delete (user as any).forceResetPassword
  // ... rest of function

Additionally, getRawGlobalUsers() at line 101 should also strip oauth2 alongside its existing password/forceResetPassword stripping for defense in depth.