GraphQL Tools provides utilities for building, stitching, and mocking GraphQL schemas. Prior to 1.1.35, the executor-legacy-ws buildWSLegacyExecutor() function hardcodes TLS certificate rejection off for Node.js connections to wss:// endpoints. Applications using the executor directly, or url-loader with SubscriptionProtocol.LEGACYWS, can therefore accept an attacker-controlled certificate when a network-positioned attacker intercepts the connection. Authentication material in connectionParams or headers can be disclosed, and subscription data can be modified. Browser WebSocket clients are unaffected because browsers enforce certificate validation. This issue is fixed in version 1.1.35.