Four issues from adversarial review of the block-scoped <style> feature:
1. (Critical) transformBlock() recursed once per @media/@supports/@container
nesting level with no cap -- ~7000 nested rules blew the call stack, and
nothing between a Custom HTML block's toHtml() and the publish pipeline
catches exceptions, so this took down the whole page's publish and
crashed the live editor on every keystroke. Added MAX_NESTING_DEPTH=20
(pass the body through unscoped beyond it) and wrapped scopeCss() so it
never throws on any input, matching repairOrphanNodes's existing
contract. Caught and fixed a variable-shadowing bug in my own first pass
at this: the new depth parameter was silently shadowed by a pre-existing
`let depth` used for brace-matching in the same block, which would have
defeated the cap with no type error.
2. (Important) FORCE_BODY: true was unconditional, but it isn't a no-op for
style-free input: it also changes how the parser preserves whitespace
after a LEADING html comment, which this repo's own fixture starts with.
Verified via a raw byte-diff against HtmlBlock.tsx@6a9b227 (extracted
verbatim, run standalone against real dompurify+jsdom) that the fixture
gained bytes. Fixed by applying FORCE_BODY only when the input has a
real (non-comment) <style> tag to rescue -- confirmed empirically that
this is a true no-op for every other input. Pinned the old output as a
checked-in regression fixture and added a raw toBe() diff test.
3. (Important) scopeStyleBlocks() wasn't idempotent -- pasting previously
published/exported output into a fresh block nested a second wrapper
and re-prefixed every selector. Added isAlreadyScoped(), which detects
a lone root wrapper whose <style> content is already a no-op under
scopeCss for that wrapper's own class (reusing scopeCss's own
idempotency guarantee) and leaves it untouched.
4. (Minor) Documented, not fixed: the 32-bit scope-id hash is
brute-forceable (CSS-only impact, same trust tier as other accepted
risks here), and DOMPurify's SAFE_FOR_XML silently drops an entire
<style> block when its content merely looks tag-like (e.g.
content: "<Read More>").
1155/1155 tests passing (was 1141), tsc clean.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
<style> was previously in FORBID_TAGS and stripped entirely. It's now
allowed, but its CSS is rewritten by a new hand-rolled scoper
(src/utils/scope-css.ts) so a customer's rules only match inside their own
block's wrapper -- never leak out and restyle the rest of the page. The
wrapper div (class="whp-html-<hash>") is only emitted when a block actually
has surviving <style> content, so blocks that don't use it stay
byte-identical to before this change.
Key findings, both covered by tests:
- DOMPurify's body-only serialization silently drops a <style> tag that
appears before any other content in a block (the HTML5 parser implicitly
places it in <head>, which DOMPurify never looks at). Fixed with
FORCE_BODY: true.
- DOMPurify does not sanitize CSS declaration values at all (expression(),
behavior:, url() to any host all pass through verbatim) -- @import is
stripped explicitly by scopeCss() since it's the one CSS-level
exfiltration/fetch vector in scope here.
Scope identifier reuses the existing djb2 stableHash() from utils/escape.ts
(already used for this exact class of problem) over the block's own `code`
string -- deterministic, no node id, no Math.random/Date.now.
1141/1141 tests passing (was 1077), tsc clean.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
shadowdaoandClaude Opus 5