Clarification 1.2.1: How requirement apply to Single Page Applications (SPA) architectures

[ajayojha]

Rule: 1.2.1 - Verify that output encoding for an HTTP response, HTML document, or XML document is relevant for the context required...”

In most of the cases the Output encoding is primary responsibility of the client-side JavaScript framework, not the backend.

[elarlang]

Correct output encoding is required one way or another. If you don't use output encoding mechanism, you need to focus on V3.2 requirements instead.

I don't see a problem here.

[ajayojha]

I have refer the V3.2 requirement, but still have question - how to "verify" 1.2.1 when responsibilities shift to the client as the current wording assumes the server-side rendering flow?

[elarlang]

Your context seems to be HTML (only). For that situation, if the output is displayed using other mechanisms, you just don't need this requirement for that.

At the same time, the SPA layer needs information that is provided by server-side component, and this one also needs to be in the correct format if XML or JSON is used.

The requirement says:

.. to avoid changing the message or document structure.

I think the intention for this is clear.

[ajayojha]

Your context seems to be HTML (only).

My concern is about verification methodology, not about HTML vs non-HTML.

if the output is displayed using other mechanisms, you just don't need this requirement for that.

I think there is ambiguity in the statement. Modern applications use multiple rendering models (SPA/CSR, SSR, SSG, hybrid approaches) In these cases, it is unclear which requirement should be applied for correct output encoding and how it should verify.

I think ASVS 1.2.1 assumes a monolithic SSR model, If HTML isn’t rendered on the server, the requirement becomes irrelevant.

[elarlang]

Each application owner should be able to understand which requirements apply to the application.

[ajayojha]

Each application owner should be able to understand which requirements apply to the application.

Please answer the questions below. If the application owner is not sure whether the requirement applies, due to ambiguous wording.

1. Based on the current wording, how should 1.2.1 be verified when encoding is performed client-side?
2. What is the scope of 1.2.1, does it apply only to server-rendered applications, or to client-rendered applications as well?
3. If the requirement applies, how should it be interpreted and verified in SPA or multi-render models?
4. Modern applications use multiple rendering models (SPA/CSR, SSR, SSG, hybrid). In these cases, how should it be verified?

[elarlang]

The answers are written in the first response: #3292 (comment)

[ajayojha]

I re-analyzed pointing out comment, along with the suggested requirement. I am sharing my understanding and concerns below:

The scope of requirement 1.2.1 is limited to server-generated HTTP responses, server-generated HTML, and server-generated XML. Please correct me if I am wrong.

Now, coming to the comment you wrote:

Correct output encoding is required one way or another.

Since this ticket is primarily discussing requirement 1.2.1, the phrase “one way or another” may be true in general security terms, but it is inaccurate within the scope of 1.2.1 requirement. The requirement explicitly mandates encoding only in HTTP responses / server-rendered documents. Therefore, in this context, there is only one way; “another way” does not apply.

or if I interpret the comment in this manner "encoding must be correct somewhere" then this is not sufficient, because it doesn't answer:

1. which requirement applies.
2. how to verify it
3. where encoding must happen in modern architectures.

If you don't use output encoding mechanism

I am keen to follow ASVS requirements, and also understand the important of output encoding as without a proper output encoding mechanism it is not possible to secure the application.

you need to focus on V3.2 requirements instead.

Here is my brief understanding of the V3 requirements; please correct me if I am wrong:

1. 3.2.1 does not ensure correct contextual encoding.
2. 3.2.2 covers safe text rendering. This overlaps somewhat with contextual output encoding on the client side, but only for raw-text injection.
3. 3.2.3 focuses on DOM clobbering, which is unrelated to encoding or escaping.

I have reviewed the other requirements as well, but I believe the cases below are not covered. If they are covered, please correct me and share the requirement numbers so I can correct my understanding:

1. SPA DOM insertion, template engines, and client-side contextual handling.
2. Unsafe bypass APIs (e.g., dangerouslySetInnerHTML).
3. JSON-to-DOM contextual encoding issues.
4. Context-specific client-side encoding functions.

I am sharing the questions again which are unanswered so far, would be great if you can answer each of the question:

1. Based on the current wording, how should 1.2.1 be verified when encoding is performed client-side?
2. What is the scope of 1.2.1, does it apply only to server-rendered applications, or to client-rendered applications as well?
3. If the requirement applies, how should it be interpreted and verified in SPA or multi-render models?
4. Modern applications use multiple rendering models (SPA/CSR, SSR, SSG, hybrid). In these cases, how should it be verified?

[elarlang]

When you opened the issue, you stated:

In most of the cases the Output encoding is primary responsibility of the client-side JavaScript framework, not the backend.

And now:

The scope of requirement 1.2.1 is limited to server-generated HTTP responses, server-generated HTML, and server-generated XML. Please correct me if I am wrong.

It is not limited to server-side - in case you build something dynamically in JavaScript and don't use special libraries for that, you need to use that defence as well. It is not ASVS's business to say which precise method you need to use, ASVS only says that whatever you choose, you need to achieve a secure result.

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The requirement explicitly mandates encoding only in HTTP responses / server-rendered documents.

Let me quote the requirement:

#	Description	Level
1.2.1	Verify that output encoding for an HTTP response, HTML document, or XML document is relevant for the context required, such as encoding the relevant characters for HTML elements, HTML attributes, HTML comments, CSS, or HTTP header fields, to avoid changing the message or document structure.	1

"HTTP response" is listed as "one of those things" that must have correct output encoding to avoid changing the message or document structure.

So, your quote or fact is clearly incorrect.

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I have reviewed the other requirements as well, but I believe the cases below are not covered. If they are covered, please correct me and share the requirement numbers so I can correct my understanding:

What is the precise problem with those and how they are not covered by "apply by context" or "use correct encoding"? You always have one of them and we have requirement for both.

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Anyway, when I try to answer your question, I feel that I'm just going to repeat the answers I have already provided. If those did not help you, repeating those answers will not help either. It only causes an endless queue of new questions, and I can not see any intent or will to solve any of the open issues. So I clearly limit my time put into such issues, as I can not see any point or progress. And "for some reason", no one else has the will to provide any answers here as well.

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As you like answers from @jmanico , you can ask the same feedback from him.

[ajayojha]

What is the precise problem with those and how they are not covered by "apply by context" or "use correct encoding"? You always have one of them and we have requirement for both.

Please refer the cases.

I can not see any intent or will to solve any of the open issues. So I clearly limit my time put into such issues, as I can not see any point or progress. And "for some reason", no one else has the will to provide any answers here as well.

I think, In a collaborative discussion, questions and answers lead to a better conclusion, also in open-source communication, the correct move is NOT to prove the other person wrong. [NOT COPIED FROM CHATGPT :) ]