violentmonkey: potential bugs in `/src/injected/web/util-web.js`

• Number.prototype.toString and window.isFinite can be replaced
• isArray is broken (isArray({splice:()=>{},length:0}) returns true, web page can delete Array.prototype.splice)
• escMap inherits from Object.prototype (web page can Object.prototype['\u0000']='fake escape')
• web page can open('/').Object.prototype.__defineGetter__('defineAs',()=>alert('???')); (maybe that’s intended)

fix (doesn’t fix isArray and defineAs):

• replace

  const { isFinite } = global; // eslint-disable-line no-restricted-properties
  const { toString: numberToString } = 0;
  

  with

  const isFinite=(()=>{
    'use strict';//need to be strict mode because (function(){isFinite({toString:function(){alert(arguments.callee.caller)}})})() alerts null
    var inf=1/0,ninf=-inf;
    return x=>(x=+x)==x&&inf!=x&&ninf!=x;
  })();
  

• replace

  const escMap = {
    '"': '\\"',
    '\\': '\\\\',
    '\b': '\\b',
    '\f': '\\f',
    '\n': '\\n',
    '\r': '\\r',
    '\t': '\\t',
  };
  const escRE = /[\\"\u0000-\u001F\u2028\u2029]/g; // eslint-disable-line no-control-regex
  const escFunc = m => escMap[m] || `\\u${(m::charCodeAt(0) + 0x10000)::numberToString(16)::slice(1)}`;
  

  with

  const jsStrEsc=s=>{
    var c,l=s.length,i=0,hex='0123456789ABCDEF',out='"';
    while(l>i)switch(c=s[i++]){
      case '"':out+='\\"';continue;
      case '\\':out+='\\\\';continue;
      case '\b':out+='\\b';continue;
      case '\f':out+='\\f';continue;
      case '\n':out+='\\n';continue;
      case '\r':out+='\\r';continue;
      case '\t':out+='\\t';continue;
      case '\u2028':out+='\\u2028';continue;
      case '\u2029':out+='\\u2029';continue;
      default:
        if('\u001F'<c){
          out+=c;
          continue;
        }
        c=c::charCodeAt(0);//String.prototype.charCodeAt can be replaced
        out+='\\u00'+
          hex[c>>4]+
          hex[15&c];
    }
    return out+'"';
  };
  

• replace

      res = `"${value::replace(escRE, escFunc)}"`;
  

  with

      res = jsStrEsc(value);