JSFiddle - React, Tailwind, and code Playground

HTML

<iframe id="wikipedia" data-src="https://pt.wikipedia.org/wiki/Constituição">

</iframe>

CSS

html, body {
  overflow: hidden;
}

html, body, iframe {
  margin: 0px;
  padding: 0px;
  border: 0px none transparent;
  width: 100%;
  height: 100%;
  box-sizing: border-box;
}

JavaScript

var CORSFrame = function (iFrame) {
  var self = this;
  this.onload = null;
  this.iFrame = iFrame;

  var httpRequest = new XMLHttpRequest();
  httpRequest.open("GET", self.corsProxy + self.iFrame.dataset.src, false);
  httpRequest.addEventListener("readystatechange", function (event) {
    if (httpRequest.readyState == 4) {
      if (httpRequest.status == 200) {
        var template = document.createElement("template");
        template.innerHTML = httpRequest.responseText;
        var content = template.content.getElementById("content");
        var blob = new Blob(['<meta charset="utf-8">' + content.outerHTML], { 
          type: 'text/html;' 
        });
        
        var bUrl = URL.createObjectURL(blob);
        self.iFrame.src = bUrl;
      }
    }
  });
  httpRequest.send();
}
CORSFrame.prototype.corsProxy = "http://crossorigin.me/";

var iFrames = document.querySelectorAll("iframe[data-src]");
[].forEach.call(iFrames, function (iFrame, indice) {  
  var corsFrame = new CORSFrame(iFrame);
  iFrame.addEventListener("load", function (event) {
    var doc = iFrame.contentWindow.document;    
    doc.body.style.backgroundColor = "black"
    doc.body.style.color = "white";
  })
});