给body的background设置backdrop-filter：blur()后，原来设置position: fixed的元素都跟着页面动起来了。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
.box {
background-color: blue;
width: 100px;
height: 100px;
position: fixed;
top: 10px;
left: 10px;
}
body {
background: url(images/test.jpg) no-repeat fixed;
backdrop-filter: blur(5px);
background-size: cover;
}
</style>
</head>
<body>
<div class="box"></div>
<p>Lorem, ipsum.</p>
<p>Sunt, quia!</p>
<p>Reprehenderit, quibusdam?</p>
<p>Possimus, praesentium.</p>
<p>Voluptatibus, ratione?</p>
<p>Et, at!</p>
<p>Delectus, reprehenderit.</p>
<p>Possimus, vel?</p>
<p>Ipsam, quam.</p>
<p>Porro, iusto.</p>
<p>A, id.</p>
<p>Exercitationem, soluta!</p>
<p>Doloribus, aperiam?</p>
<p>Odio, cum.</p>
<p>Id, possimus.</p>
<p>Nesciunt, sequi!</p>
<p>Earum, accusamus?</p>
<p>Qui, cum.</p>
<p>Quis, repellat.</p>
<p>Iste, libero?</p>
<p>Quo, doloribus?</p>
<p>Obcaecati, quia.</p>
<p>Totam, labore!</p>
<p>Est, repellendus.</p>
<p>Voluptas, minus!</p>
<p>Ullam, dolores?</p>
<p>Aliquid, beatae!</p>
<p>Totam, quibusdam?</p>
<p>Libero, impedit.</p>
<p>Atque, odit!</p>
</body>
</html>
