Fix prototype pollution vulerability

Author: jdesrosiers

lib/index.js

@@ -314,8 +314,10 @@ const applySegment = (value, segment, cursor = "") => {
     throw TypeError(`Value at '${cursor}' is a ${typeof value} and does not have property '${segment}'`);
   } else {
     const computedSegment = computeSegment(value, segment);
-    // value could also be an array, but this appeases the type system
-    return /** @type API.JsonObject */ (value)[computedSegment];
+    if (Object.hasOwn(value, computedSegment)) {
+      // value could also be an array, but this appeases the type system
+      return /** @type API.JsonObject */ (value)[computedSegment];
+    }
   }
 };