Description

Webhook Authorization Header Returned in Plaintext via API

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "2.7",
  "pubDate": "2026-08-13T17:17:28.973Z",
  "pubdate": "2026-08-13T17:17:28.973Z",
  "executiveSummary": "An information disclosure vulnerability exists where webhook authorization headers are returned in plaintext via the application programming interface. This security flaw allows unauthorized actors to intercept sensitive authentication credentials transmitted during API interactions.\nThe primary impact of this vulnerability involves the exposure of sensitive secret tokens, API keys, or bearer credentials utilized for webhook verification and integration authorization. Compromise of these cryptographic credentials permits malicious actors to impersonate legitimate webhook services, forge incoming webhook events, or pivot into integrated third-party systems.\nThe affected systems comprise application programming interfaces responsible for configuring, managing, or returning webhook integration metadata and configuration payloads. Risk implications are severe, as exposed authorization headers violate core cryptographic protection standards for secrets management in transit and at rest.\nAttacker capabilities include the passive or active sniffing of API responses containing configuration objects where sensitive authentication headers are improperly serialized and reflected without redaction or encryption. Exploitation requirements generally necessitate valid API access or insufficient authorization controls that allow retrieval of webhook configuration endpoints, enabling unauthorized extraction of sensitive authentication parameters.",
  "technicalDetails": "The root cause of this vulnerability lies in insecure API serialization practices where backend controllers or data transfer objects fail to sanitize sensitive header fields before transmitting configuration payloads to clients. Specifically, webhook integration schemas include authorization parameters—such as HTTP Authorization headers containing bearer tokens or basic authentication strings—directly within the standard API response body.\nThe vulnerable component involves the API endpoint handlers responsible for reading, updating, or returning webhook subscription configurations. When a client queries these endpoints, the application serializes the entire database model or internal configuration dictionary, which inappropriately retains sensitive secret material rather than masking or omitting it.\nThe attack flow proceeds in a stepwise manner: First, an authenticated user or an attacker with access to the API configuration endpoints submits a standard GET or POST request to retrieve webhook subscription details. Second, the backend application queries the persistent data store for the webhook configuration, retrieving the plaintext authorization credentials stored for dispatch verification. Third, the API response serializer packs this sensitive data into a JSON or XML payload without applying necessary filtering, hashing, or redaction functions. Finally, the response is transmitted over the network containing the authorization header in cleartext, where it can be captured via man-in-the-middle (MitM) positioning or direct API interrogation by low-privileged accounts.\nAuthentication and privilege requirements depend on the API's access control enforcement; however, the vulnerability is particularly critical if low-privileged users can read administrative webhook configurations, or if unauthenticated endpoints improperly expose management functionalities. Network exposure is broad, affecting any deployment where the API is accessible over HTTP/HTTPS without strict response-filtering middleware.\nPost-exploitation impact encompasses unauthorized access to downstream systems that trust the exposed webhook credentials, event spoofing, data injection, and potential lateral movement across interconnected microservices or third-party webhooks relying on the same shared secret."
}