cryptpad/www/pad/disable-base64.js

( function() {
    CKEDITOR.plugins.add('blockbase64', {
        init: function (editor) {

            var replaceImgText = function (html) {
                var ret = html.replace( /<img[^>]*src="data:image\/(bmp|dds|gif|jpg|jpeg|png|psd|pspimage|tga|thm|tif|tiff|yuv|ai|eps|ps|svg);base64,.*?"[^>]*>/gi,
                    function () {
                        console.error("Direct image paste is not allowed.");
                        return '';
                });
                return ret;
            };

            /*var chkImg = function () {
                // don't execute code if the editor is readOnly
                if (editor.readOnly) {
                    return;
                }

                setTimeout( function() {
                    editor.document.$.body.innerHTML = replaceImgText(editor.document.$.body.innerHTML);
                },100);
            };

            editor.on('contentDom', function () {
                // For Firefox
                editor.document.on('drop', chkImg);
                // For IE
                editor.document.getBody().on('drop', chkImg);
            });*/

            editor.on('paste', function(e) {
                var html = e.data.dataValue;
                if (!html) { return; }
                e.data.dataValue = replaceImgText(html);
            });

        }
    });
})();