[bug]: Refused to load the stylesheet because it violates the following Content Security Policy

[sergeycherepanov]

Describe the bug
I enabled the SASS support by the official guide and it works in debug/watch mode. But after yarn build && yarn start the styles where broken and the console says:

Refused to load the stylesheet 'blob:http://0.0.0.0:8080/8e286dcc-c3ec-445d-aab8-0ad3e322891a' because it violates the following Content Security Policy directive: "style-src 'self' https: 'unsafe-inline' https://m2.hm2.space/". Note that 'style-src-elem' was not explicitly set, so 'style-src' is used as a fallback.

To reproduce

1. Enable the saas support by the following guide: https://magento.github.io/pwa-studio/tutorials/enable-sass-less-support/
2. Rename the index.css to index.scss and import in the index.js file.
3. Build the project by the following command: yarn build
4. Start the project by the following command: yarn start

Expected behavior

No errors in the console and styles loaded properly.

Please complete the following device information:

• Device [PC, Mac]:
• OS [MacOs, Windows 10]:
• Browser [Chrome]:
• Browser Version [e.g. 22]:
• Magento Version: 2.4
• PWA Studio Version: 8
• NPM version npm -v: 6.14.10
• Node Version node -v: v12.20.1

Please let us know what packages this bug is in regards to:

• venia-concept
• venia-ui
• pwa-buildpack
• peregrine
• pwa-devdocs
• upward-js
• upward-spec
• create-pwa

[m2-assistant]

Hi @sergeycherepanov. Thank you for your report.
To help us process this issue please make sure that you provided sufficient information.

Please, add a comment to assign the issue: @magento I am working on this

---

• Join Magento Community Engineering Slack and ask your questions in #github channel.

[sirugh]

Thanks for reporting this! For what it's worth the headers are defined in the upward-security-headers extension. The solution will probably have to do with modifying the headers to allow blob.

[sirugh]

@magento export issue to JIRA project PWA as Bug

[github-jira-sync-bot]

✅ Jira issue (https://jira.corp.magento.com/browse/PWA-1387) is successfully created for this issue.