How do Blade and Twig automatically escape output by default, and why is this an important security feature?

Both Blade and Twig automatically escape variable output by default, meaning any special HTML characters within a displayed value are converted into their safe text equivalents before being rendered, which protects against cross site scripting attacks where a malicious value, such as user submitted text containing embedded script tags, could otherwise be rendered as actual executable code within the page rather than harmless plain text, and this automatic protection happens without the developer needing to remember to manually escape every single displayed value themselves.

{{-- Blade automatically escapes this --}}
{{ $userComment }}

{# Twig automatically escapes this #}
{{ user_comment }}