fix(markdown): block /\ protocol-relative redirect in safeUrl - #47
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safeUrl allowed "/path" but blocked "//host" to keep links on-site. It missed the backslash form: browsers normalise \ to /, so href="/\evil.com" resolves to "//evil.com" — an off-site redirect from user-authored content blocks. \ isn't HTML-escaped and isn't matched by the link regex's \s, so it reaches safeUrl. Reject a leading /\ as well as //; add regression tests.
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What
safeUrlallows/pathbut blocks//hostto keep links on-site. It misses the backslash form: browsers normalise\to/, sohref="/\evil.com"resolves to//evil.com— an off-site (open) redirect.Why it matters
renderMarkdownrenders owner/content-block markdown on tenant pages.\is not HTML-escaped and is not whitespace, so the link/image regex captures it and it reachessafeUrl. Verified:[click](/\evil.com)-><a href="/\evil.com">(browser ->//evil.com)-><img src="/\evil.com">[ok](//evil.com)is correctly blocked; the\form slipped past the same guard.Fix
Reject a leading
/\as well as//:/^\/(?![/\\])/. Legit/path,https:,mailto:and#anchorare unchanged.Tests
Added
tests/markdown.test.mjs: backslash link + image blocked,//still blocked, legit relative/absolute still work,javascript:still blocked.node --test tests/markdown.test.mjspasses; no other tests affected.