See the original report in https://github.com/facebook/react/issues/10772#issuecomment-333242375.

The problem is that SVG is case sensitive, and so naïvely setting `tabIndex` and relying on insensitivity won't work with it.

The good news is it seems like `tabindex` is the only valid [SVG attribute](https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute) with this problem. We just missed it because it applies both to HTML and SVG.

I think the fix is to add it back to the whitelist. 
<div onunknownevent="alert(&quot;hack&quot;)" />,
        1,
      );
      expect(e.getAttribute('onunknownevent')).toBe(null);
    });
  });
  describe('elements and children', function() {
    function expectNode(node, type, value) {
      expect(node).not.toBe(null);
      expect(node.nodeType).toBe(type);
      expect(node.nodeValue).toMatch(value);
    }
    function expectTextNode(node, text) {
      expectNode(node, TEXT_NODE_TYPE, text);
    }
    describe('text children', function() {
      itRenders('a div with text', async render => {
        const e = await render(<div>Text</div>);
        expect(e.tagName).toBe('DIV');
        expect(e.childNodes.length).toBe(1);
        expectNode(e.firstChild, TEXT_NODE_TYPE, 'Text');
      });
      itRenders('a div with text with flanking whitespace', async render => {
        
        const e = await render(<div>  Text </div>);
        expect(e.childNodes.length).toBe(1);
        expectNode(e.childNodes[0], TEXT_NODE_TYPE, '  Text ');
      });
      itRenders('a div with an empty text child', async render => {
        const e = await render(<div>{''}</div>);