The fourth bypass found in this review, and the one no lexer fix
reaches: sanitizing runs on the stored body, but safeTemplateReplace
rewrites it afterwards, so the string that was validated is not the
string that is sent.
A conditional inside a style attribute can delete the very quoting that
made a url() inert:
style="--x:x{{#if company_name}}'{{/if}};background:url(https://evil…)"
At write time the url() genuinely sits inside a CSS string and is
correctly left alone. Expanding the conditional for a recipient with no
company name removes both quotes and the background goes live —
confirmed end to end against the real functions.
The style-attribute pass now runs again on the substituted output.
Substitution cannot introduce a `"` (values are HTML-escaped), so the
attribute match still holds. body_css is not substituted, so the
<style> block cannot be rewritten after its check and needs nothing.
This is the case the removed newsletter pass had been covering. Rather
than reinstating a second definition of "disallowed", the one definition
now runs at both points where the content changes.
Refs #1264
Paul Nothaft
027afb6086