With the Clear Floats Button plugin enabled in WordPress 4.3.1, if I add a <div> with an id attribute the id attribute is stripped away by the visual editor:

1. Switch to the text editor and add `<div id="foo" class="bar">text</div>`.
2. Switch to the visual editor.
3. Switch back to the text editor. The markup now looks like `<div class="bar">text</div>`.

It looks like the problem is in line 56 of clear-floats-button.php:

$init['extended_valid_elements'] = 'div[clear|style|class]';

I assume this is overwriting a default configuration which allows div[id], although I can't see where the default configuration is coming from. This plugin should at least append to the existing allowed attributes rather than overwrite them.