Json5 version 0.5.1 represents a minor but important update to the Json5 library, building upon the foundation laid by version 0.5.0, a library designed to offer a more developer-friendly JSON experience for ES5 environments. The core functionality, described as "JSON for the ES5 era," remains consistent between the two versions, indicating that the fundamental purpose of providing a less strict and more human-readable JSON alternative hasn't changed.
The key differences lie within the development dependencies. Version 0.5.1 sees updates to several crucial tools used in the library's development lifecycle: gulp-jshint, jshint, and jshint-stylish. Specifically, gulp-jshint moves from version 2.0.0 to 2.0.1, jshint advances from 2.9.1 to 2.9.3, and jshint-stylish is updated from 2.1.0 to 2.2.1. Mocha is also updated from version ^2.4.5 to ^3.1.0. These updates signal improvements in code linting and style enforcement, potentially leading to a more robust and maintainable codebase. For developers using Json5, these upgrades translate to a more reliable library with potentially fewer bugs and better adherence to coding standards. While the core API and functionality likely remain the same, the updated development dependencies ensure the project continues to evolve and adapt to newer tools and best practices, enhancing the overall quality and longevity of the Json5 library. Using newer versions of testing frameworks can mean that there are more and better tests in the library.
All the vulnerabilities related to the version 0.5.1 of the package
Prototype Pollution in JSON5 via Parse Method
The parse method of the JSON5 library before and including version 2.2.1 does not restrict parsing of keys named __proto__, allowing specially crafted strings to pollute the prototype of the resulting object.
This vulnerability pollutes the prototype of the object returned by JSON5.parse and not the global Object prototype, which is the commonly understood definition of Prototype Pollution. However, polluting the prototype of a single object can have significant security impact for an application if the object is later used in trusted operations.
This vulnerability could allow an attacker to set arbitrary and unexpected keys on the object returned from JSON5.parse. The actual impact will depend on how applications utilize the returned object and how they filter unwanted keys, but could include denial of service, cross-site scripting, elevation of privilege, and in extreme cases, remote code execution.
This vulnerability is patched in json5 v2.2.2 and later. A patch has also been backported for json5 v1 in versions v1.0.2 and later.
Suppose a developer wants to allow users and admins to perform some risky operation, but they want to restrict what non-admins can do. To accomplish this, they accept a JSON blob from the user, parse it using JSON5.parse, confirm that the provided data does not set some sensitive keys, and then performs the risky operation using the validated data:
const JSON5 = require('json5');
const doSomethingDangerous = (props) => {
if (props.isAdmin) {
console.log('Doing dangerous thing as admin.');
} else {
console.log('Doing dangerous thing as user.');
}
};
const secCheckKeysSet = (obj, searchKeys) => {
let searchKeyFound = false;
Object.keys(obj).forEach((key) => {
if (searchKeys.indexOf(key) > -1) {
searchKeyFound = true;
}
});
return searchKeyFound;
};
const props = JSON5.parse('{"foo": "bar"}');
if (!secCheckKeysSet(props, ['isAdmin', 'isMod'])) {
doSomethingDangerous(props); // "Doing dangerous thing as user."
} else {
throw new Error('Forbidden...');
}
If the user attempts to set the isAdmin key, their request will be rejected:
const props = JSON5.parse('{"foo": "bar", "isAdmin": true}');
if (!secCheckKeysSet(props, ['isAdmin', 'isMod'])) {
doSomethingDangerous(props);
} else {
throw new Error('Forbidden...'); // Error: Forbidden...
}
However, users can instead set the __proto__ key to {"isAdmin": true}. JSON5 will parse this key and will set the isAdmin key on the prototype of the returned object, allowing the user to bypass the security check and run their request as an admin:
const props = JSON5.parse('{"foo": "bar", "__proto__": {"isAdmin": true}}');
if (!secCheckKeysSet(props, ['isAdmin', 'isMod'])) {
doSomethingDangerous(props); // "Doing dangerous thing as admin."
} else {
throw new Error('Forbidden...');
}