Sanitizing User Input Before Adding It to the Dom in JavaScript

Sanitizing user input before adding it to the DOM in Javascript

Never use escape(). It's nothing to do with HTML-encoding. It's more like URL-encoding, but it's not even properly that. It's a bizarre non-standard encoding available only in JavaScript.

If you want an HTML encoder, you'll have to write it yourself as JavaScript doesn't give you one. For example:

function encodeHTML(s) {
    return s.replace(/&/g, '&').replace(/</g, '<').replace(/"/g, '"');
}

However whilst this is enough to put your user_id in places like the input value, it's not enough for id because IDs can only use a limited selection of characters. (And % isn't among them, so escape() or even encodeURIComponent() is no good.)

You could invent your own encoding scheme to put any characters in an ID, for example:

function encodeID(s) {
    if (s==='') return '_';
    return s.replace(/[^a-zA-Z0-9.-]/g, function(match) {
        return '_'+match[0].charCodeAt(0).toString(16)+'_';
    });
}

But you've still got a problem if the same user_id occurs twice. And to be honest, the whole thing with throwing around HTML strings is usually a bad idea. Use DOM methods instead, and retain JavaScript references to each element, so you don't have to keep calling getElementById, or worrying about how arbitrary strings are inserted into IDs.

eg.:

function addChut(user_id) {
    var log= document.createElement('div');
    log.className= 'log';
    var textarea= document.createElement('textarea');
    var input= document.createElement('input');
    input.value= user_id;
    input.readonly= True;
    var button= document.createElement('input');
    button.type= 'button';
    button.value= 'Message';

    var chut= document.createElement('div');
    chut.className= 'chut';
    chut.appendChild(log);
    chut.appendChild(textarea);
    chut.appendChild(input);
    chut.appendChild(button);
    document.getElementById('chuts').appendChild(chut);

    button.onclick= function() {
        alert('Send '+textarea.value+' to '+user_id);
    };

    return chut;
}

You could also use a convenience function or JS framework to cut down on the lengthiness of the create-set-appends calls there.

ETA:

I'm using jQuery at the moment as a framework

OK, then consider the jQuery 1.4 creation shortcuts, eg.:

var log= $('<div>', {className: 'log'});
var input= $('<input>', {readOnly: true, val: user_id});
...

The problem I have right now is that I use JSONP to add elements and events to a page, and so I can not know whether the elements already exist or not before showing a message.

You can keep a lookup of user_id to element nodes (or wrapper objects) in JavaScript, to save putting that information in the DOM itself, where the characters that can go in an id are restricted.

var chut_lookup= {};
...

function getChut(user_id) {
    var key= '_map_'+user_id;
    if (key in chut_lookup)
        return chut_lookup[key];
    return chut_lookup[key]= addChut(user_id);
}

(The _map_ prefix is because JavaScript objects don't quite work as a mapping of arbitrary strings. The empty string and, in IE, some Object member names, confuse it.)

Input sanitization in ReactJS

It's sanitized by default, you don't need a sanitization method unless you are using dangerouslySetInnerHTML which is not the case.

Simplest way to escape all special chars of user input text

My inital answer would be to create a options element and set the innerText instead of innerHTML

but since u use jQuery...

$('#x').prepend($('<option>', {text: userInput}))

Sanitizing input to stick into a hidden input value with jQuery

Instead of doing this with html strings, create an actual element and set it's value property using val().

You can sanitize any possible html out of it by first inserting the string into a content element as text and retrieving it as text.

Note that the value property does not get rendered in the html the same as value attribute does so quotes are not an issue

$("#myButton").on('click', function(){
    // sanitize any html in the existing input
    var myValue = $('<div>', {text:$('#myInput').val())).text();
    listSize++;    
    // create new elements
    var $listItem = $("<li>",{text: myValue});
    // set value of input after creating the element
    var $input = $('<input>',{ type:'hidden', name:'foo'+listSize}).val(myValue);
    //append input to list item
    $listItem.append($input);
    // append in dom
    $("ol.myList").append($listItem);
});

Do I need to sanitize user input before posting to query_posts?

The parse_query contains general sanitation, not specific ones to your ( unknown ) case or data type validation. The docs do not mention that because it assumes that programmers will do that .
The CODEX is a great tool - that I use every day, but you must understand that it is not 100% correct, nor completed . It is more of a specific guidlines .

The rest is up to one`s common sense.

I suggest you read HERE and also HERE‌​ if you want codex reference for data sanitation and validation - and also for a list of specific data type functions that are built-in into wordpress.

So the answer to your direct question is simply " YES " . you should sanitize / escape , and "NO" , you should assume it is not safe ( even if it is, or you assume that it is ) .

Do I have to explicitly sanitize input fields in Angular 6?

I appreciate your questions, it may be useful to others. Under no circumstances should the backed ever trust the front end, no framework, no custom library, nothing. If someone can exploit, inject, or otherwise harass your backed, they will, period. They will do so bypassing any front end framework or library and make direct requests to the endpoint, masquerading as anything necessary to do so.

And as @etarhan said, read this: https://angular.io/guide/security

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