Crash server with query parameter

@@ -4,7 +4,8 @@ Jump directly to a version:
 
 | 4.x                                  |
 |--------------------------------------|
-| [**4.10.2 (latest release)**](#4102) |
+| [**4.10.3 (latest release)**](#4103) |
+| [4.10.2](#4102)                      |
 | [4.10.1](#4101)                      |
 | [4.10.0](#4100)                      |
 | [4.5.2](#452)                        |
@@ -93,14 +94,16 @@ Jump directly to a version:
 ___
 
 ## Unreleased (Master Branch)
-[Full Changelog](https://github.com/parse-community/parse-server/compare/4.10.2...master)
+[Full Changelog](https://github.com/parse-community/parse-server/compare/4.10.3...master)
+
 ### Breaking Changes
 - Improved schema caching through database real-time hooks. Reduces DB queries, decreases Parse Query execution time and fixes a potential schema memory leak. If multiple Parse Server instances connect to the same DB (for example behind a load balancer), set the [Parse Server Option](https://parseplatform.org/parse-server/api/master/ParseServerOptions.html) `databaseOptions.enableSchemaHooks: true` to enable this feature and keep the schema in sync across all instances. Failing to do so will cause a schema change to not propagate to other instances and re-syncing will only happen when these instances restart. The options `enableSingleSchemaCache` and `schemaCacheTTL` have been removed. To use this feature with MongoDB, a replica set cluster with [change stream](https://docs.mongodb.com/manual/changeStreams/#availability) support is required. (Diamond Lewis, SebC) [#7214](https://github.com/parse-community/parse-server/issues/7214)
 - Added file upload restriction. File upload is now only allowed for authenticated users by default for improved security. To allow file upload also for Anonymous Users or Public, set the `fileUpload` parameter in the [Parse Server Options](https://parseplatform.org/parse-server/api/master/ParseServerOptions.html) (dblythy, Manuel Trezza) [#7071](https://github.com/parse-community/parse-server/pull/7071)
 - Removed [parse-server-simple-mailgun-adapter](https://github.com/parse-community/parse-server-simple-mailgun-adapter) dependency; to continue using the adapter it has to be explicitly installed (Manuel Trezza) [#7321](https://github.com/parse-community/parse-server/pull/7321)
 - Remove support for MongoDB 3.6 which has reached its End-of-Life date and PostgreSQL 10 (Manuel Trezza) [#7315](https://github.com/parse-community/parse-server/pull/7315)
 - Remove support for Node 10 which has reached its End-of-Life date (Manuel Trezza) [#7314](https://github.com/parse-community/parse-server/pull/7314)
 - Remove S3 Files Adapter from Parse Server, instead install separately as `@parse/s3-files-adapter` (Manuel Trezza) [#7324](https://github.com/parse-community/parse-server/pull/7324)
+
 ### Notable Changes
 - Added Parse Server Security Check to report weak security settings (Manuel Trezza, dblythy) [#7247](https://github.com/parse-community/parse-server/issues/7247)
 - EXPERIMENTAL: Added new page router with placeholder rendering and localization of custom and feature pages such as password reset and email verification (Manuel Trezza) [#7128](https://github.com/parse-community/parse-server/pull/7128)
@@ -147,6 +150,12 @@ ___
 - Add CI check to add changelog entry (Manuel Trezza) [#7512](https://github.com/parse-community/parse-server/pull/7512)
 - Refactor: uniform issue templates across repos (Manuel Trezza) [#7528](https://github.com/parse-community/parse-server/pull/7528)
 
+## 4.10.3
+[Full Changelog](https://github.com/parse-community/parse-server/compare/4.10.2...4.10.3)
+
+### Security Fixes
+- Validate `explain` query parameter to avoid a server crash due to MongoDB bug [NODE-3463](https://jira.mongodb.org/browse/NODE-3463) (Kartal Kaan Bozdogan) [GHSA-xqp8-w826-hh6x](https://github.com/parse-community/parse-server/security/advisories/GHSA-xqp8-w826-hh6x)
+
 ## 4.10.2
 [Full Changelog](https://github.com/parse-community/parse-server/compare/4.10.1...4.10.2)
 

@@ -37,6 +37,54 @@ describe('Parse.Query testing', () => {
     });
   });
 
+  it_only_db('mongo')('gracefully handles invalid explain values', async () => {
+    // Note that anything that is not truthy (like 0) does not cause an exception, as they get swallowed up by ClassesRouter::optionsFromBody
+    const values = [1, 'yolo', { a: 1 }, [1, 2, 3]];
+    for (const value of values) {
+      try {
+        await request({
+          method: 'GET',
+          url: `http://localhost:8378/1/classes/_User?explain=${value}`,
+          json: true,
+          headers: masterKeyHeaders,
+        });
+        fail('request did not throw');
+      } catch (e) {
+        // Expect that Parse Server did not crash
+        expect(e.code).not.toEqual('ECONNRESET');
+        // Expect that Parse Server validates the explain value and does not crash;
+        // see https://jira.mongodb.org/browse/NODE-3463
+        equal(e.data.code, Parse.Error.INVALID_QUERY);
+        equal(e.data.error, 'Invalid value for explain');
+      }
+      // get queries (of the form '/classes/:className/:objectId' cannot have the explain key, see ClassesRouter.js)
+      // so it is enough that we test find queries
+    }
+  });
+
+  it_only_db('mongo')('supports valid explain values', async () => {
+    const values = [
+      false,
+      true,
+      'queryPlanner',
+      'executionStats',
+      'allPlansExecution',
+      // 'queryPlannerExtended' is excluded as it only applies to MongoDB Data Lake which is currently not available in our CI environment
+    ];
+    for (const value of values) {
+      const response = await request({
+        method: 'GET',
+        url: `http://localhost:8378/1/classes/_User?explain=${value}`,
+        json: true,
+        headers: masterKeyHeaders,
+      });
+      expect(response.status).toBe(200);
+      if (value) {
+        expect(response.data.results.ok).toBe(1);
+      }
+    }
+  });
+
   it('searching for null', function (done) {
     const baz = new TestObject({ foo: null });
     const qux = new TestObject({ foo: 'qux' });

@@ -108,6 +108,23 @@ const mongoSchemaFromFieldsAndClassNameAndCLP = (
   return mongoObject;
 };
 
+function validateExplainValue(explain) {
+  if (explain) {
+    // The list of allowed explain values is from node-mongodb-native/lib/explain.js
+    const explainAllowedValues = [
+      'queryPlanner',
+      'queryPlannerExtended',
+      'executionStats',
+      'allPlansExecution',
+      false,
+      true,
+    ];
+    if (!explainAllowedValues.includes(explain)) {
+      throw new Parse.Error(Parse.Error.INVALID_QUERY, 'Invalid value for explain');
+    }
+  }
+}
+
 export class MongoStorageAdapter implements StorageAdapter {
   // Private
   _uri: string;
@@ -578,6 +595,7 @@ export class MongoStorageAdapter implements StorageAdapter {
     query: QueryType,
     { skip, limit, sort, keys, readPreference, hint, caseInsensitive, explain }: QueryOptions
   ): Promise<any> {
+    validateExplainValue(explain);
     schema = convertParseSchemaToMongoSchema(schema);
     const mongoWhere = transformWhere(className, query, schema);
     const mongoSort = _.mapKeys(sort, (value, fieldName) =>
@@ -756,6 +774,7 @@ export class MongoStorageAdapter implements StorageAdapter {
     hint: ?mixed,
     explain?: boolean
   ) {
+    validateExplainValue(explain);
     let isPointerField = false;
     pipeline = pipeline.map(stage => {
       if (stage.$group) {

@@ -657,7 +657,7 @@ RestQuery.prototype.runFind = function (options = {}) {
   return this.config.database
     .find(this.className, this.restWhere, findOptions, this.auth)
     .then(results => {
-      if (this.className === '_User' && findOptions.explain !== true) {
+      if (this.className === '_User' && !findOptions.explain) {
         for (var result of results) {
           cleanResultAuthData(result);
         }
@@ -866,7 +866,7 @@ function includePath(config, auth, response, path, restOptions = {}) {
           return set;
         }
       }
-      if (i == (keyPath.length - 1)) {
+      if (i == keyPath.length - 1) {
         set.add(keyPath[i]);
       }
       return set;