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Fix/link identity provider token #2069

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Fix/link identity provider token #2069

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9231ae0
fix(auth): detect provider-only link callback
samarth212 Jan 28, 2026
0a1649d
test(auth): cover provider-token-only link callback
samarth212 Jan 28, 2026
c30e189
fix(auth): use _useSession for provider-only callbacks
samarth212 Jan 28, 2026
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29 changes: 28 additions & 1 deletion packages/core/auth-js/src/GoTrueClient.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -2052,6 +2052,28 @@ export default class GoTrueClient {
} = params

if (!access_token || !expires_in || !refresh_token || !token_type) {
if (provider_token || provider_refresh_token) {
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@depthfirst-app depthfirst-app Bot Jan 28, 2026

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🟠 Severity: HIGH

CSRF/Token Injection Vulnerability: This code allows arbitrary provider_token and provider_refresh_token values from URL fragments to be injected into existing sessions without validation. An attacker can craft a malicious URL and trick users into visiting it, causing attacker-controlled provider tokens to be merged into the victim's session. There's no CSRF protection (state parameter), origin validation, or server-side verification that these tokens are legitimate.
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💡 Fix Suggestion

Suggestion: This vulnerability requires server-side validation and CSRF protection. Implement the following multi-step fix: (1) Add a 'state' parameter to the OAuth flow that's generated server-side and validated on callback. Store the state parameter securely (e.g., in session storage with CSRF token) before initiating the OAuth flow. (2) Before merging provider_token and provider_refresh_token into the session, validate the state parameter from the URL matches the stored value. (3) Send the provider tokens to the auth server endpoint (e.g., POST to /token/verify) to verify they were issued for the current authenticated user before accepting them. (4) Only merge the tokens if both state validation and server-side token verification succeed. (5) Consider rejecting provider-token-only callbacks entirely if they're not expected in the linkIdentity flow, or require them to come with additional proof of authenticity from the auth server.

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@samarth212 samarth212 Jan 28, 2026 •
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Updated to use _useSession in _getSessionFromURL for provider‑token‑only callbacks to honor the documented locking contract.

We only merge provider tokens when a valid session already exists (user must be signed in), and the callback is handled by the Supabase auth redirect flow. Still, if maintainers want stricter validation or a type=link gate, I can add that in a follow‑up.

const { data: sessionData, error: sessionError } = await this._useSession(
async (result) => result
)
if (sessionError) throw sessionError
if (!sessionData.session) {
throw new AuthImplicitGrantRedirectError('No session defined in URL')
}

const session: Session = {
...sessionData.session,
provider_token,
provider_refresh_token,
}

// Remove tokens from URL
window.location.hash = ''
this._debug('#_getSessionFromURL()', 'clearing window.location.hash')

return this._returnResult({ data: { session, redirectType: params.type }, error: null })
}
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throw new AuthImplicitGrantRedirectError('No session defined in URL')
}

Expand Down Expand Up @@ -2126,7 +2148,12 @@ export default class GoTrueClient {
if (typeof this.detectSessionInUrl === 'function') {
return this.detectSessionInUrl(new URL(window.location.href), params)
}
return Boolean(params.access_token || params.error_description)
return Boolean(
params.access_token ||
params.error_description ||
params.provider_token ||
params.provider_refresh_token
)
}

/**
Expand Down
26 changes: 26 additions & 0 deletions packages/core/auth-js/test/GoTrueClient.browser.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -346,6 +346,32 @@ describe('Callback URL handling', () => {
expect(session?.refresh_token).toBe('test-refresh-token')
})

it('should attach provider token when callback only includes provider tokens', async () => {
window.location.href =
'http://localhost:9999/callback#provider_token=provider-token&provider_refresh_token=provider-refresh&type=link'

const expiresAt = Math.floor(Date.now() / 1000) + 3600
storedSession = JSON.stringify({
access_token: 'existing-access-token',
refresh_token: 'existing-refresh-token',
expires_in: 3600,
expires_at: expiresAt,
token_type: 'bearer',
user: { id: 'test-user' },
})

const client = getClientWithSpecificStorage(mockStorage)
await client.initialize()

const {
data: { session },
} = await client.getSession()
expect(session).toBeDefined()
expect(session?.access_token).toBe('existing-access-token')
expect(session?.provider_token).toBe('provider-token')
expect(session?.provider_refresh_token).toBe('provider-refresh')
})

it('should handle error in callback URL', async () => {
// Set up URL with error parameters
window.location.href =
Expand Down
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