The preview framed the page public URL, which for a custom domain is cross
origin and blocked by the admin document CSP frame-src. Point the iframe at the
same-origin public path while the frame chrome still shows the public URL.
The form only enforced the length cap, so CSS with an external url() or @import
passed client validation and was rejected by the server. Add the same tokenizer
based check with the same error message so it is caught inline before submit.
Detect custom domains by comparing the request host to the app host and apply
the tightened CSP there too, not just on the public path. Run the middleware
before express.static so static-served root documents get the header, and keep
helmet after static so its default-src does not block custom domain API calls.
Layer a stricter Content-Security-Policy on the /status/public document so
custom CSS cannot load external images, fonts, or stylesheets. Browsers
enforce the intersection of all CSP headers, so this only narrows the public
status page and never loosens the global policy, while keeping the app's
Google Fonts. Browser-enforced backstop behind the validator.
Replace the regex/escape-normalizer with @csstools/css-tokenizer (already
present transitively). Tokenizing resolves comments, hex escapes, and line
continuations into the real value before scanning, so obfuscated forms (a
scheme split by a line continuation or hex escape) cannot slip past. Scan
url-tokens and string-tokens to cover url(), quoted @import, and string-form
image functions. Add regression tests for the bypasses.
Reject status page custom CSS containing @import or a url() / image-set()
/ image() / cross-fade() whose target is http(s) or protocol-relative,
while allowing data: and relative URLs. The check normalizes comments and
CSS escapes first so obfuscated forms cannot slip past. Enforced in the
create/update body validation.
Alex Holliday
sanmaxdev
Arnaud GRIMBERT
Buco7854