alfresco-ng2-components/lib/content-services/upload/components/upload-button.component.scss

.adf {
    &-upload-button-file-container input {
        cursor: pointer;
        height: 100%;
        right: 0;
        opacity: 0;
        position: absolute;
        top: 0;
        width: 300px;
        z-index: 4;
    }
}