how to avoid the google chrome extension affect the web page

I am develop a google chrome extension in the 6.x-master, after I install the extension, seems the extension css affect the original web page. when I access stackoverflow, the web page was unnormal:

I packge the extension js and css using splitChunks like this:

optimization: {
    splitChunks: {
      cacheGroups: {
        commons1: {
          name: 'commons1',
          chunks: 'all',
          minChunks: 1,
          test(module,chunks){
            for (const chunk of module.chunksIterable) {
              if (chunk.name && /(popup|content)/.test(chunk.name)) {
                   return true;
              }
            }
            return false;
          }
        },
        commons2: {
          name: 'commons2',
          chunks: 'all',
          minChunks: 1,
          test(module,chunks){
            for (const chunk of module.chunksIterable) {
              if (chunk.name && /(options|commons1)/.test(chunk.name)) {
                   return true;
              }
            }
            return false;
          }
        },
        commons3: {
          name: 'commons3',
          chunks: 'all',
          minChunks: 1,
          test(module,chunks){
            for (const chunk of module.chunksIterable) {
              if (chunk.name && /(bg|commons2)/.test(chunk.name)) {
                   return true;
              }
            }
            return false;
          }
        },
      }
    }
  },

The legacy code works fine util I migrate from older version to new, I removed the legacy CommonChunk to splitChunks. what should I do to make the extension independent and not affect the original web page? BTW, this is the full webpack config of the extension:

const path = require('path');
const webpack = require( 'webpack' ) ,
  ExtractTextPlugin = require( 'extract-text-webpack-plugin' );

module.exports = {
  entry : {
    bg : './src/background-scripts/' ,
    content : ['./src/content-scripts/firefox-fix.js', './src/content-scripts/'] ,
    options : [
      './src/options/'
    ],
    popup : './src/popup/' ,
    'bs-lite' : './src/public/bootstrap-lite.scss'
  } ,
  output : {
    path : path.resolve(__dirname, '../src/bundle') ,
    filename : '[name].js'
  } ,
  module : {
    rules : [
      {
        test : /\.js$/ ,
        exclude : [ /node_modules(?!(\/|\\?\\)(translation\.js|selection-widget|connect\.io|chrome-env)\1)/ ] ,
        loader : 'babel-loader'
      } ,
      {
        test : /\.woff$/ ,
        loader : 'file-loader' ,
        query : {
          name : '[name].[ext]'
        }
      } ,
      {
        test : /\.html$/ ,
        loader : 'vue-html-loader'
      } , 
      {
        test : /\.(css|scss)$/ ,
        use: ExtractTextPlugin.extract({
          fallback :'style-loader',
          use: [
            'css-loader',
            {
              loader: 'sass-loader',
              options: {
                implementation: require('sass')
              }
            }]
        })
      }
    ]
  },
  optimization: {
    splitChunks: {
      cacheGroups: {
        commons1: {
          name: 'commons1',
          chunks: 'all',
          minChunks: 1,
          test(module,chunks){
            for (const chunk of module.chunksIterable) {
              if (chunk.name && /(popup|content)/.test(chunk.name)) {
                   return true;
              }
            }
            return false;
          }
        },
        commons2: {
          name: 'commons2',
          chunks: 'all',
          minChunks: 1,
          test(module,chunks){
            for (const chunk of module.chunksIterable) {
              if (chunk.name && /(options|commons1)/.test(chunk.name)) {
                   return true;
              }
            }
            return false;
          }
        },
        commons3: {
          name: 'commons3',
          chunks: 'all',
          minChunks: 1,
          test(module,chunks){
            for (const chunk of module.chunksIterable) {
              if (chunk.name && /(bg|commons2)/.test(chunk.name)) {
                   return true;
              }
            }
            return false;
          }
        },
      }
    }
  },
  plugins : [
    new ExtractTextPlugin( {
      filename: '[name].css',
      allChunks: true
     })
  ]
};

what should I do to found which part of the google chrome extension affect the web page?