Escape bootstrapScriptContent for javascript embedding into HTML

The previous escape was for Text into HTML and breaks script contents. The new escaping ensures that the script contents cannot prematurely close the host script tag by escaping script open and close string sequences using a unicode escape substitution.

packages/react-dom/src/__tests__/escapeScriptForBrowser-test.js

@@ -0,0 +1,107 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @emails react-core
+ */
+
+'use strict';
+
+let React;
+let ReactDOMFizzServer;
+let Stream;
+
+function getTestWritable() {
+  const writable = new Stream.PassThrough();
+  writable.setEncoding('utf8');
+  const output = {result: '', error: undefined};
+  writable.on('data', chunk => {
+    output.result += chunk;
+  });
+  writable.on('error', error => {
+    output.error = error;
+  });
+  const completed = new Promise(resolve => {
+    writable.on('finish', () => {
+      resolve();
+    });
+    writable.on('error', () => {
+      resolve();
+    });
+  });
+  return {writable, completed, output};
+}
+
+describe('escapeScriptForBrowser', () => {
+  beforeEach(() => {
+    jest.resetModules();
+    React = require('react');
+    ReactDOMFizzServer = require('react-dom/server');
+    Stream = require('stream');
+  });
+
+  it('"<[Ss]cript" strings are replaced with unicode escaped lowercase s or S depending on case', () => {
+    const {writable, output} = getTestWritable();
+    const {pipe} = ReactDOMFizzServer.renderToPipeableStream(<div />, {
+      bootstrapScriptContent:
+        '"prescription pre<scription preScription pre<Scription"',
+    });
+    pipe(writable);
+    jest.runAllTimers();
+    expect(output.result).toMatch(
+      '<div></div><script>"prescription pre<\\u0073cription preScription pre<\\u0053cription"</script>',
+    );
+  });
+
+  it('"</[Ss]cript" strings are replaced with encoded lowercase s or S depending on case', () => {
+    const {writable, output} = getTestWritable();
+    const {pipe} = ReactDOMFizzServer.renderToPipeableStream(<div />, {
+      bootstrapScriptContent:
+        '"prescription pre</scription preScription pre</Scription"',
+    });
+    pipe(writable);
+    jest.runAllTimers();
+    expect(output.result).toMatch(
+      '<div></div><script>"prescription pre</\\u0073cription preScription pre</\\u0053cription"</script>',
+    );
+  });
+
+  it('"[Ss]cript", "/[Ss]cript", "<[Ss]crip", "</[Ss]crip" strings are not escaped', () => {
+    const {writable, output} = getTestWritable();
+    const {pipe} = ReactDOMFizzServer.renderToPipeableStream(<div />, {
+      bootstrapScriptContent:
+        '"Script script /Script /script <Scrip <scrip </Scrip </scrip"',
+    });
+    pipe(writable);
+    jest.runAllTimers();
+    expect(output.result).toMatch(
+      '<div></div><script>"Script script /Script /script <Scrip <scrip </Scrip </scrip"</script>',
+    );
+  });
+
+  it('matches case insensitively', () => {
+    const {writable, output} = getTestWritable();
+    const {pipe} = ReactDOMFizzServer.renderToPipeableStream(<div />, {
+      bootstrapScriptContent: '"<sCrIpT <ScripT </scrIPT </SCRIpT"',
+    });
+    pipe(writable);
+    jest.runAllTimers();
+    expect(output.result).toMatch(
+      '<div></div><script>"<\\u0073CrIpT <\\u0053cripT </\\u0073crIPT </\\u0053CRIpT"</script>',
+    );
+  });
+
+  it('does not escape <, >, &, \\u2028, or \\u2029 characters', () => {
+    const {writable, output} = getTestWritable();
+    const {pipe} = ReactDOMFizzServer.renderToPipeableStream(<div />, {
+      bootstrapScriptContent: '"<, >, &, \u2028, or \u2029"',
+    });
+    pipe(writable);
+    jest.runAllTimers();
+    expect(output.result).toMatch(
+      '<div></div><script>"<, >, &, \u2028, or \u2029"</script>',
+    );
+  });
+});

packages/react-dom/src/server/ReactDOMServerFormatConfig.js

@@ -52,6 +52,7 @@ import {validateProperties as validateUnknownProperties} from '../shared/ReactDO
 import warnValidStyle from '../shared/warnValidStyle';
 
 import escapeTextForBrowser from './escapeTextForBrowser';
+import escapeScriptForBrowser from './escapeScriptForBrowser';
 import hyphenateStyleName from '../shared/hyphenateStyleName';
 import hasOwnProperty from 'shared/hasOwnProperty';
 import sanitizeURL from '../shared/sanitizeURL';
@@ -102,7 +103,7 @@ export function createResponseState(
   if (bootstrapScriptContent !== undefined) {
     bootstrapChunks.push(
       inlineScriptWithNonce,
-      stringToChunk(escapeTextForBrowser(bootstrapScriptContent)),
+      stringToChunk(escapeScriptForBrowser(bootstrapScriptContent)),
       endInlineScript,
     );
   }

packages/react-dom/src/server/escapeScriptForBrowser.js

@@ -0,0 +1,37 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {checkHtmlStringCoercion} from 'shared/CheckStringCoercion';
+
+const scriptRegex = /(<\/|<)(s)(cript)/gi;
+const scriptReplacer = (match, prefix, s, suffix) =>
+  `${prefix}${subsitutions[s]}${suffix}`;
+const subsitutions = {
+  s: '\\u0073',
+  S: '\\u0053',
+};
+
+/**
+ * Escapes javascript for embedding into HTML.
+ *
+ * @param {*} scriptText Text value to escape.
+ * @return {string} An escaped string.
+ */
+function escapeScriptForBrowser(scriptText) {
+  if (typeof scriptText === 'boolean' || typeof scriptText === 'number') {
+    // this shortcircuit helps perf for types that we know will never have
+    // special characters, especially given that this function is used often
+    // for numeric dom ids.
+    return '' + scriptText;
+  }
+  if (__DEV__) {
+    checkHtmlStringCoercion(scriptText);
+  }
+  return ('' + scriptText).replace(scriptRegex, scriptReplacer);
+}
+
+export default escapeScriptForBrowser;