Authorizer: Password reset token theft and full auth token redirect via unvalidated redirect_uri

Hi,

I found that 6 endpoints in Authorizer accept a user-controlled redirect_uri and append sensitive tokens to it without validating the URL against AllowedOrigins. The OAuth /app handler validates redirect_uri at http_handlers/app.go:46, but the GraphQL mutations and verify_email handler skip validation entirely. An attacker can steal password reset tokens, magic link tokens, and full auth sessions (access_token + id_token + refresh_token) by pointing redirect_uri to their server. Verified against HEAD (commit 73679fa).

Affected Endpoints

1. ForgotPassword (internal/graphql/forgot_password.go:76-77) - password reset tokens
2. MagicLinkLogin (internal/graphql/magic_link_login.go:150-151) - magic link auth tokens
3. Signup (internal/graphql/signup.go:211-212) - email verification tokens
4. InviteMembers (internal/graphql/invite_members.go:90-91) - invitation tokens
5. OAuthLoginHandler (internal/http_handlers/oauth_login.go:18-20) - OAuth redirect stored in state
6. VerifyEmailHandler (internal/http_handlers/verify_email.go:27,178) - full auth tokens (access + id + refresh)

Root Cause

Because these 6 endpoints completely lack the validators.IsValidOrigin() check, this vulnerability bypasses secure configurations. Even if a production administrator strictly configures AllowedOrigins to ["https://my-secure-app.com"], an attacker can still steal tokens by passing https://attacker.com to these specific GraphQL mutations. The validation only exists in the /app OAuth handler, not in any of the GraphQL mutations.

In forgot_password.go:76-77, the user-supplied redirect_uri is accepted without validation:

if strings.TrimSpace(refs.StringValue(params.RedirectURI)) != "" {
    redirectURI = refs.StringValue(params.RedirectURI)
}

The reset token is appended to this URL at internal/utils/common.go:77:

func GetForgotPasswordURL(token, redirectURI string) string {
    verificationURL := redirectURI + "?token=" + token
    return verificationURL
}

Compare with the OAuth flow at internal/http_handlers/app.go:46 which validates correctly:

if !validators.IsValidOrigin(redirectURI, h.Config.AllowedOrigins) {
    c.JSON(400, gin.H{"error": "invalid redirect url"})
    return
}