export declare function resolveHost(hostname: string): Promise<string[]>;
/**
 * Validates a webhook URL to prevent SSRF attacks by blocking internal/private IP addresses
 * Should be called when saving webhook URLs and before sending webhooks
 *
 * Security Note: This validation has a Time-of-Check-Time-of-Use (TOCTOU) vulnerability
 * where DNS can change between validation and actual HTTP request. For maximum security,
 * the HTTP client should also implement IP blocking at connection time.
 */
export declare function validateWebhookURL(urlString: string): Promise<void>;
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