Use DOMPurify to sanitize and mitigate XSS attacks

package.json

@@ -47,6 +47,7 @@
     "array-move": "^4.0.0",
     "browserfs": "^1.4.3",
     "classnames": "^2.3.2",
+    "dompurify": "^3.1.6",
     "flexboxgrid": "^6.3.1",
     "flexboxgrid-helpers": "^1.1.3",
     "hastscript": "^9.0.0",
@@ -109,6 +110,7 @@
     "@testing-library/jest-dom": "^6.0.0",
     "@testing-library/react": "^14.0.0",
     "@testing-library/user-event": "^14.4.3",
+    "@types/dompurify": "^3.0.5",
     "@types/estree": "^1.0.5",
     "@types/gapi": "^0.0.44",
     "@types/gapi.auth2": "^0.0.57",

src/commons/Markdown.tsx

@@ -1,5 +1,6 @@
 import { Classes } from '@blueprintjs/core';
 import classNames from 'classnames';
+import DOMPurify from 'dompurify';
 import React from 'react';
 import { Converter } from 'showdown';
 
@@ -24,7 +25,12 @@ const Markdown: React.FC<Props> = props => {
   return (
     <div
       className={classNames(props.className ? props.className : 'md', Classes.RUNNING_TEXT)}
-      dangerouslySetInnerHTML={{ __html: converter.makeHtml(props.content) }}
+      dangerouslySetInnerHTML={{
+        __html: DOMPurify.sanitize(converter.makeHtml(props.content), {
+          USE_PROFILES: { html: true },
+          ADD_ATTR: ['target']
+        })
+      }}
     />
   );
 };

src/commons/__tests__/__snapshots__/Markdown.tsx.snap

@@ -6,10 +6,10 @@ exports[`Markdown page renders correctly 1`] = `
   dangerouslySetInnerHTML={
     Object {
       "__html": "<p>Welcome to the Source Academy playground!</p>
-<p>The book <a href=\\"https://sourceacademy.org/sicpjs/\\" rel=\\"noopener noreferrer\\" target=\\"_blank\\"><em>Structure and Interpretation of Computer Programs, JavaScript Edition</em></a>
-uses JavaScript sublanguages that we call <a href=\\"https://docs.sourceacademy.org/\\" rel=\\"noopener noreferrer\\" target=\\"_blank\\"><em>Source</em></a>. You have chosen the sublanguage <a href=\\"https://docs.sourceacademy.org/source_1/\\" rel=\\"noopener noreferrer\\" target=\\"_blank\\"><em>Source §1</em></a>.</p>
-<p>In the editor on the left, you can use the <a href=\\"https://github.com/ajaxorg/ace/wiki/Default-Keyboard-Shortcuts\\" rel=\\"noopener noreferrer\\" target=\\"_blank\\"><em>Ace keyboard shortcuts</em></a> 
-and also the <a href=\\"https://github.com/source-academy/frontend/wiki/Source-Academy-Keyboard-Shortcuts\\" rel=\\"noopener noreferrer\\" target=\\"_blank\\"><em>Source Academy keyboard shortcuts</em></a>.</p>",
+<p>The book <a target=\\"_blank\\" rel=\\"noopener noreferrer\\" href=\\"https://sourceacademy.org/sicpjs/\\"><em>Structure and Interpretation of Computer Programs, JavaScript Edition</em></a>
+uses JavaScript sublanguages that we call <a target=\\"_blank\\" rel=\\"noopener noreferrer\\" href=\\"https://docs.sourceacademy.org/\\"><em>Source</em></a>. You have chosen the sublanguage <a target=\\"_blank\\" rel=\\"noopener noreferrer\\" href=\\"https://docs.sourceacademy.org/source_1/\\"><em>Source §1</em></a>.</p>
+<p>In the editor on the left, you can use the <a target=\\"_blank\\" rel=\\"noopener noreferrer\\" href=\\"https://github.com/ajaxorg/ace/wiki/Default-Keyboard-Shortcuts\\"><em>Ace keyboard shortcuts</em></a> 
+and also the <a target=\\"_blank\\" rel=\\"noopener noreferrer\\" href=\\"https://github.com/source-academy/frontend/wiki/Source-Academy-Keyboard-Shortcuts\\"><em>Source Academy keyboard shortcuts</em></a>.</p>",
     }
   }
 />

yarn.lock

@@ -2936,6 +2936,13 @@
   dependencies:
     "@types/ms" "*"
 
+"@types/dompurify@^3.0.5":
+  version "3.0.5"
+  resolved "https://registry.yarnpkg.com/@types/dompurify/-/dompurify-3.0.5.tgz#02069a2fcb89a163bacf1a788f73cb415dd75cb7"
+  integrity sha512-1Wg0g3BtQF7sSb27fJQAKck1HECM6zV1EB66j8JH9i3LCjYabJa0FSdiSgsD5K/RbrsR0SiraKacLB+T8ZVYAg==
+  dependencies:
+    "@types/trusted-types" "*"
+
 "@types/eslint@^7.29.0 || ^8.4.1":
   version "8.21.1"
   resolved "https://registry.yarnpkg.com/@types/eslint/-/eslint-8.21.1.tgz#110b441a210d53ab47795124dbc3e9bb993d1e7c"
@@ -3279,6 +3286,11 @@
   resolved "https://registry.yarnpkg.com/@types/stack-utils/-/stack-utils-2.0.3.tgz#6209321eb2c1712a7e7466422b8cb1fc0d9dd5d8"
   integrity sha512-9aEbYZ3TbYMznPdcdr3SmIrLXwC/AKZXQeCf9Pgao5CKb8CyHuEX5jzWPTkvregvhRJHcpRO6BFoGW9ycaOkYw==
 
+"@types/trusted-types@*":
+  version "2.0.7"
+  resolved "https://registry.yarnpkg.com/@types/trusted-types/-/trusted-types-2.0.7.tgz#baccb07a970b91707df3a3e8ba6896c57ead2d11"
+  integrity sha512-ScaPdn1dQczgbl0QFTeTOmVHFULt394XJgOQNoyVhZ6r2vLnMLJfBPd53SB52T/3G36VI1/g2MZaX0cwDuXsfw==
+
 "@types/trusted-types@^2.0.2":
   version "2.0.3"
   resolved "https://registry.yarnpkg.com/@types/trusted-types/-/trusted-types-2.0.3.tgz#a136f83b0758698df454e328759dbd3d44555311"
@@ -5950,6 +5962,11 @@ domhandler@^5.0.2, domhandler@^5.0.3:
   dependencies:
     domelementtype "^2.3.0"
 
+dompurify@^3.1.6:
+  version "3.1.6"
+  resolved "https://registry.yarnpkg.com/dompurify/-/dompurify-3.1.6.tgz#43c714a94c6a7b8801850f82e756685300a027e2"
+  integrity sha512-cTOAhc36AalkjtBpfG6O8JimdTMWNXjiePT2xQH/ppBGi/4uIpmj8eKyIkMJErXWARyINV/sB38yf8JCLF5pbQ==
+
 domutils@^1.7.0:
   version "1.7.0"
   resolved "https://registry.yarnpkg.com/domutils/-/domutils-1.7.0.tgz#56ea341e834e06e6748af7a1cb25da67ea9f8c2a"