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fix: replace invalid codepoints with U+FFFD in entity parser #353

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Merged
kjk merged 1 commit into from
Feb 17, 2026
Merged

fix: replace invalid codepoints with U+FFFD in entity parser #353

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8 changes: 8 additions & 0 deletions inline_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1325,3 +1325,11 @@ func BenchmarkSmartDoubleQuotes(b *testing.B) {
runMarkdown("this should be normal \"quoted\" text.\n", params)
}
}

func TestEntityNullByte(t *testing.T) {
// � should produce U+FFFD per CommonMark spec section 6.2
doTestsInlineParam(t, []string{
"�",
"<p>\uFFFD</p>\n",
}, TestParams{})
}
7 changes: 6 additions & 1 deletion parser/inline.go
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Original file line number Diff line number Diff line change
Expand Up @@ -817,7 +817,12 @@ func entity(p *Parser, data []byte, offset int) (int, ast.Node) {
codepoint, err = strconv.ParseUint(string(ent[2:len(ent)-1]), 10, 64)
}
if err == nil { // only if conversion was valid return here.
return end, newTextNode([]byte(string(rune(codepoint))))
r := rune(codepoint)
// Replace invalid codepoints with U+FFFD per CommonMark spec section 6.2
if r == 0 || (r >= 0xD800 && r <= 0xDFFF) || r > 0x10FFFF {
r = '\uFFFD'
}
return end, newTextNode([]byte(string(r)))
}

return end, newTextNode(ent)
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