# Improvements to JavaScript analysis ## General improvements * TypeScript 3.8 is now supported. * You can now suppress alerts using either single-line block comments (`/* ... */`) or line comments (`// ...`). * Resolution of imports has improved, leading to more results from the security queries: - Imports with the `.js` extension can now be resolved to a TypeScript file, when the import refers to a file generated by TypeScript. - Imports that rely on path-mappings from a `tsconfig.json` file can now be resolved. - Export declarations of the form `export * as ns from "x"` are now analyzed more precisely. * The analysis of sanitizers has improved, leading to more accurate results from the security queries. In particular: - Sanitizer guards now act across function boundaries in more cases. - Sanitizers can now better distinguish between a tainted value and an object _containing_ a tainted value. * Call graph construction has been improved, leading to more results from the security queries: - Calls can now be resolved to indirectly-defined class members in more cases. - Calls through partial invocations such as `.bind` can now be resolved in more cases. * Support for flow summaries has been more clearly marked as being experimental and moved to the new `experimental` folder. * Support for the following frameworks and libraries has been improved: - [chrome-remote-interface](https://www.npmjs.com/package/chrome-remote-interface) - [Electron](https://electronjs.org/) - [for-in](https://www.npmjs.com/package/for-in) - [for-own](https://www.npmjs.com/package/for-own) - [fstream](https://www.npmjs.com/package/fstream) - [Handlebars](https://www.npmjs.com/package/handlebars) - [http2](https://nodejs.org/api/http2.html) - [jQuery](https://jquery.com/) - [jsonfile](https://www.npmjs.com/package/jsonfile) - [Koa](https://www.npmjs.com/package/koa) - [lazy-cache](https://www.npmjs.com/package/lazy-cache) - [mongodb](https://www.npmjs.com/package/mongodb) - [ncp](https://www.npmjs.com/package/ncp) - [Node.js](https://nodejs.org/) - [node-dir](https://www.npmjs.com/package/node-dir) - [path-exists](https://www.npmjs.com/package/path-exists) - [pg](https://www.npmjs.com/package/pg) - [react](https://www.npmjs.com/package/react) - [recursive-readdir](https://www.npmjs.com/package/recursive-readdir) - [request](https://www.npmjs.com/package/request) - [rimraf](https://www.npmjs.com/package/rimraf) - [send](https://www.npmjs.com/package/send) - [Socket.IO](https://socket.io/) - [SockJS](https://www.npmjs.com/package/sockjs) - [SockJS-client](https://www.npmjs.com/package/sockjs-client) - [typeahead.js](https://www.npmjs.com/package/typeahead.js) - [vinyl-fs](https://www.npmjs.com/package/vinyl-fs) - [WebSocket](https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API) - [write-file-atomic](https://www.npmjs.com/package/write-file-atomic) - [ws](https://github.com/websockets/ws) ## New queries | **Query** | **Tags** | **Purpose** | |---------------------------------------------------------------------------------|-------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | Cross-site scripting through exception (`js/xss-through-exception`) | security, external/cwe/cwe-079, external/cwe/cwe-116 | Highlights potential XSS vulnerabilities where an exception is written to the DOM. Results are not shown on LGTM by default. | | Missing await (`js/missing-await`) | correctness | Highlights expressions that operate directly on a promise object in a nonsensical way, instead of awaiting its result. Results are shown on LGTM by default. | | Polynomial regular expression used on uncontrolled data (`js/polynomial-redos`) | security, external/cwe/cwe-730, external/cwe/cwe-400 | Highlights expensive regular expressions that may be used on malicious input. Results are shown on LGTM by default. | | Prototype pollution in utility function (`js/prototype-pollution-utility`) | security, external/cwe/cwe-400, external/cwe/cwe-471 | Highlights recursive assignment operations that are susceptible to prototype pollution. Results are shown on LGTM by default. | | Regular expression always matches (`js/regex/always-matches`) | correctness, regular-expressions | Highlights regular expression checks that trivially succeed by matching an empty substring. Results are shown on LGTM by default. | | Unsafe jQuery plugin (`js/unsafe-jquery-plugin`) | | Highlights potential XSS vulnerabilities in unsafely designed jQuery plugins. Results are shown on LGTM by default. | | Unnecessary use of `cat` process (`js/unnecessary-use-of-cat`) | correctness, security, maintainability | Highlights command executions of `cat` where the fs API should be used instead. Results are shown on LGTM by default. | ## Changes to existing queries | **Query** | **Expected impact** | **Change** | |--------------------------------|------------------------------|---------------------------------------------------------------------------| | Clear-text logging of sensitive information (`js/clear-text-logging`) | More results | More results involving `process.env` and indirect calls to logging methods are recognized. | | Duplicate parameter names (`js/duplicate-parameter-name`) | Fewer results | This query now ignores additional parameters that reasonably can have duplicated names. | | Expression has no effect (`js/useless-expression`) | Fewer false positive results | The query now recognizes block-level flow type annotations and ignores the first statement of a try block. | | Identical operands (`js/redundant-operation`) | Fewer results | This query now excludes cases where the operands change a value using ++/-- expressions. | | Incomplete string escaping or encoding (`js/incomplete-sanitization`) | Fewer false positive results | This query now recognizes and excludes additional cases where a single replacement is likely to be intentional. | | Incomplete URL scheme check (`js/incomplete-url-scheme-check`) | More results | This query now recognizes additional variations of URL scheme checks. | | Missing CSRF middleware (`js/missing-token-validation`) | Fewer false positive results | The query reports fewer duplicates and only flags handlers that explicitly access cookie data. | | Superfluous trailing arguments (`js/superfluous-trailing-arguments`) | Fewer results | This query now excludes cases where a function uses the `Function.arguments` value to process a variable number of parameters. | | Syntax error (`js/syntax-error`) | Lower severity | This results of this query are now displayed with lower severity. | | Unbound event handler receiver (`js/unbound-event-handler-receiver`) | Fewer false positive results | This query now recognizes additional ways event handler receivers can be bound. | | Uncontrolled command line (`js/command-line-injection`) | More results | This query now recognizes additional ways of constructing arguments to `cmd.exe` and `/bin/sh`. | | Uncontrolled data used in path expression (`js/path-injection`) | More results | This query now recognizes additional ways dangerous paths can be constructed and used. | | Use of call stack introspection in strict mode (`js/strict-mode-call-stack-introspection`) | Fewer false positive results | The query no longer flags expression statements. | | Use of password hash with insufficient computational effort (`js/insufficient-password-hash`) | Fewer false positive results | This query now recognizes and excludes additional cases that do not require secure hashing. | | Useless regular-expression character escape (`js/useless-regexp-character-escape`) | Fewer false positive results | This query now distinguishes between escapes in strings and regular expression literals. | ## Changes to libraries * The predicates `RegExpTerm.getSuccessor` and `RegExpTerm.getPredecessor` have been changed to reflect textual, not operational, matching order. This only makes a difference in lookbehind assertions, which are operationally matched backwards. Previously, `getSuccessor` would mimic this, so in an assertion `(?<=ab)` the term `b` would be considered the predecessor, not the successor, of `a`. Textually, however, `a` is still matched before `b`, and this is the order we now follow. * An extensible model of the `EventEmitter` pattern has been implemented. * Taint-tracking configurations now interact differently with the `data` flow label, which may affect queries that combine taint-tracking and flow labels. - Sources added by the 1-argument `isSource` predicate are associated with the `taint` label now, instead of the `data` label. - Sanitizers now only block the `taint` label. As a result, sanitizers no longer block the flow of tainted values wrapped inside a property of an object. To retain the old behavior, instead use a barrier, or block the `data` flow label using a labeled sanitizer.