fix(php-wasm): retry through the CORS proxy when a credentialed request resolves unauthorized by nilesh32236 · Pull Request #4462 · WordPress/wordpress-playground

nilesh32236 · 2026-10-16T09:07:39Z

Problem

fetchWithCorsProxy() only reached the cors.wordpress.net proxy from its catch block, i.e. only when the direct fetch() threw.

A host that allows CORS broadly passes preflight for a request that carries an Authorization header — but the browser still strips that header, because the request is not credentials: 'include'. So the direct fetch resolves with 401 instead of throwing. The retry never ran, and the caller was handed the 401.

The practical effect: any plugin calling a third-party REST API that needs Authorization (Stripe, OpenAI, Mailchimp, Twilio, SendGrid) silently fails forever, and nothing in the response points at the proxy path that was supposed to rescue it.

Change

The direct response is now inspected. If it is 401/403, or the request intends to pass credentials, the response is discarded and the existing proxy retry (with credentials: 'include') runs.

The predicate is deliberately narrow — it only applies when the developer opted in via X-Cors-Proxy-Allowed-Request-Headers — so behaviour is byte-for-byte unchanged for every other request. The opt-in header's value is now also lower-cased and trimmed before matching, so an Authorization entry (capitalised, as headers usually are) is honoured.

No new code path was invented: this reuses the retry, body handling, multipart wrapping and firewall detection that already existed.

Testing

npx nx test php-wasm-web-service-worker — new cases added to fetch-with-cors-proxy.spec.ts:

	Before	After
Proxy spec	`expected "fetch" to be called 2 times, but got 1 times`	`OK` (25/25)
Package	—	34/34

Reviewer note

I kept the "should I retry?" condition to the credential case on purpose. Retrying every resolved 4xx would double traffic for genuine client errors, so this only retries when the developer has declared the header and the response looks like a credential rejection.

Summary by CodeRabbit

Bug Fixes
- Requests rejected by cross-origin restrictions can retry through the configured proxy. Eligible 401 and 403 responses can also retry when the request explicitly allows the relevant headers; otherwise, the direct response is returned.
- Allowed-header matching now ignores surrounding whitespace and capitalization, making opt-in behavior consistent across header formats.
- Proxy retries include credentials only when authorization or cookie headers are explicitly allowed.

…st resolves unauthorized fetchWithCorsProxy() only fell back to the cors.wordpress.net proxy from the catch block, so it ran on a thrown fetch. A host that allows CORS broadly passes preflight for a request carrying an Authorization header, but the browser still strips that header because the request is not credentials: 'include'. The direct fetch therefore RESOLVES with 401 instead of throwing, the retry never ran, and the caller was handed the 401. Plugins that call a third-party REST API needing Authorization (Stripe, OpenAI, Mailchimp, Twilio, SendGrid) silently failed forever. The direct response is now inspected: if it is 401/403, or the request intends to pass credentials, it is discarded and the existing proxy retry (credentials: 'include') runs. The predicate stays narrow - it only applies when the developer opted in through the X-Cors-Proxy-Allowed-Request-Headers header - so behaviour is unchanged for every other request. That header's value is also normalised to lower-case before matching, so an `Authorization` entry is honoured.

coderabbitai · 2026-10-16T09:09:00Z

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packages/php-wasm/web-service-worker/src/lib/fetch-with-cors-proxy.ts

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📝 Walkthrough

fetchWithCorsProxy now evaluates resolved direct responses as well as fetch failures. It retries through the CORS proxy for opted-in requests that receive a 401 or 403. Tests cover an opted-in authorization retry and a request without proxy opt-in.

Changes: Credentialed CORS proxy retry

Layer / File(s)	Summary
Determine when to retry `packages/php-wasm/web-service-worker/src/lib/fetch-with-cors-proxy.ts`	Allowed header names are trimmed and matched case-insensitively. An opted-in request retries after a direct 401 or 403. The direct response body is cancelled before retry.
Prepare and validate the proxy retry `packages/php-wasm/web-service-worker/src/lib/fetch-with-cors-proxy.ts`, `packages/php-wasm/web-service-worker/src/test/fetch-with-cors-proxy.spec.ts`	The proxy retry retains multipart handling, request-body preparation, and HTTP proxy buffering. It includes credentials when authorization or cookie is allowed, and checks for the proxy identification header. Tests cover a 401 retry with authorization opt-in and a 401 response without opt-in.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix · Severity of issue fixed: Medium

Sequence Diagram(s)

sequenceDiagram
  participant Caller
  participant fetchWithCorsProxy
  participant DirectFetch
  participant CORSProxy
  Caller->>fetchWithCorsProxy: Submit request
  fetchWithCorsProxy->>DirectFetch: Fetch request directly
  DirectFetch-->>fetchWithCorsProxy: Reject or return response
  fetchWithCorsProxy->>CORSProxy: Retry after a fetch error or eligible 401/403
  CORSProxy-->>fetchWithCorsProxy: Return proxy response
  fetchWithCorsProxy-->>Caller: Return response

Suggested reviewers: adamziel

Merge Risk: ⚪ Minimal · up to 1a9af

Opted-in unauthorized requests can retry through the proxy without retrying successful responses. No merge-blocking issue is established.

Pre-merge checks: 5

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the primary change: retrying credentialed requests through the CORS proxy when a direct request resolves with an unauthorized response.
Linked Issues check		Issue `#3559` requires opted-in requests to reach the CORS proxy when direct fetch resolves with a credential-related 401. The change detects resolved 401 and 403 responses, normalizes `X-Cors-Proxy-All…
Out of Scope Changes check		The source change updates direct-response handling, opt-in header matching, and the existing proxy retry path. The test changes cover the new retry and the no-opt-in behavior. Multipart handling, requ…
Docstring Coverage		Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 2 files.

Full details: Linked Issues check

Explanation

Issue #3559 requires opted-in requests to reach the CORS proxy when direct fetch resolves with a credential-related 401. The change detects resolved 401 and 403 responses, normalizes X-Cors-Proxy-Allowed-Request-Headers values, and reuses the existing proxy retry with credentials: 'include' for authorization or cookie. The added tests verify the 401 retry and preserve direct 401 behavior without opt-in.

Full details: Out of Scope Changes check

Explanation

The source change updates direct-response handling, opt-in header matching, and the existing proxy retry path. The test changes cover the new retry and the no-opt-in behavior. Multipart handling, request-body handling, and firewall detection remain within the same proxy flow. No unrelated change is shown.

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Inline comments:
Review comments at
@packages/php-wasm/web-service-worker/src/lib/fetch-with-cors-proxy.ts:
- Around line 126-129: Update shouldRetryResolvedResponse in the direct-response
flow to retry only when directResponseLooksUnauthorized, while retaining the
corsProxyAllowedHeaders check. Before retrying, cancel directResponse.body and
ignore cancellation failures so the discarded response is cleaned up.

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packages/php-wasm/web-service-worker/src/lib/fetch-with-cors-proxy.ts
packages/php-wasm/web-service-worker/src/test/fetch-with-cors-proxy.spec.ts

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github-actions Bot added [Aspect] Browser [Aspect] Service Worker [Package][@php-wasm] Web [Type] Bug An existing feature does not function as intended labels Oct 16, 2026

coderabbitai Bot reviewed Oct 16, 2026

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Comment thread packages/php-wasm/web-service-worker/src/lib/fetch-with-cors-proxy.ts Outdated

fix(php-wasm): limit CORS-proxy retries to unauthorized responses

1a9af42

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fix(php-wasm): retry through the CORS proxy when a credentialed request resolves unauthorized - #4462

fix(php-wasm): retry through the CORS proxy when a credentialed request resolves unauthorized#4462
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nilesh32236:fix/3559-cors-proxy-credential-retry

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