**Do you want to request a *feature* or report a *bug*?**
Bug

**What is the current behavior?**
The code is: 
```
class App extends React.Component {
  render() {
    return (
      <div>
        <sCript>alert('Hi');</sCript>
        <script>alert('script 2: this should not execute');</script>
      </div>
    );
  }
}
```
the script in ` <sCript>alert('Hi');</sCript>` executed.
![s_ 2018-10-11 15 56 00](https://user-images.githubusercontent.com/2378632/46789074-3a1ee500-cd6e-11e8-8b0f-1ab172857f7c.png)

**If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem. Your bug will get fixed much faster if we can run your code and it doesn't have dependencies other than React. Paste the link to your JSFiddle (https://jsfiddle.net/Luktwrdm/) or CodeSandbox (https://codesandbox.io/s/new) example below:**

Demo in codepen: https://codepen.io/zenany/pen/rqmPYq

**What is the expected behavior?**

`<sCript>alert('Hi');</sCript>` should not processed as code, this may cause security risk.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**

versions:
```
  "dependencies": {
    "react": "^16.5.2",
    "react-dom": "^16.5.2",
  },
```
browser: firefox, chrome


enableDeprecatedFlareAPI,
  enableTrustedTypesIntegration,
  enableModernEventSystem,
} from 'shared/ReactFeatureFlags';
import {
  legacyListenToEvent,
  legacyTrapBubbledEvent,
} from '../events/DOMLegacyEventPluginSystem';
import {listenToEvent} from '../events/DOMModernPluginEventSystem';
let didWarnInvalidHydration = false;
let didWarnScriptTags = false;
const DANGEROUSLY_SET_INNER_HTML = 'dangerouslySetInnerHTML';
const SUPPRESS_CONTENT_EDITABLE_WARNING = 'suppressContentEditableWarning';
const SUPPRESS_HYDRATION_WARNING = 'suppressHydrationWarning';
const AUTOFOCUS = 'autoFocus';
const CHILDREN = 'children';
const STYLE = 'style';
const HTML = '__html';
const DEPRECATED_flareListeners = 'DEPRECATED_flareListeners';
const {html: HTML_NAMESPACE} = Namespaces;
let warnedUnknownTags;
let suppressHydrationWarning;
let validatePropertiesInDevelopment;
let warnForTextDifference;
let warnForPropDifference;
let warnForExtraAttributes;
let warnForInvalidEventListener;
let canDiffStyleForHydrationWarning;
let normalizeMarkupForTextOrAttribute;
let normalizeHTML;