1 file changed, 17 insertions, 2 deletions
diff --git a/custom/extensions/about-render.lua b/custom/extensions/about-render.lua
index 3c92252..4e4b50b 100644
--- a/custom/extensions/about-render.lua
+++ b/custom/extensions/about-render.lua
@@ -157,7 +157,8 @@ end
 -- The page renders untrusted repository content. Every run of text goes out
 -- through cgit's html_txt, every attribute value through html_attr or, for a
 -- path in the tree, html_url_path, and every link target through safe_url
--- first. html() only ever gets literal tag scaffolding.
+-- first. html() only ever gets literal tag scaffolding and the character
+-- references whose shape the markdown grammar checked.
 
 local emit_inline
 
@@ -166,6 +167,8 @@ emit_inline = function(list)
 		local kind = node.kind
 		if kind == "text" then
 			html_txt(node.text)
+		elseif kind == "reference" then
+			html(node.text)
 		elseif kind == "break" then
 			html("<br>")
 		elseif kind == "code" then
@@ -294,7 +297,7 @@ if has_lpeg then
 	local whitespace = S(" \t\r\n\f\v")
 	local eol = P(-1)
 
-	local marker = S("`![*_<\\")
+	local marker = S("`![*_<\\&")
 	local punctuation = S("!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~")
 	local url_char = 1 - S(")") - whitespace
 	-- Bound the link and image inner scans. Without a cap a readme of
@@ -323,6 +326,9 @@ if has_lpeg then
 	local function node_image()
 		return { kind = "image" }
 	end
+	local function node_reference(text)
+		return { kind = "reference", text = text }
+	end
 	local function node_autolink(url)
 		return { kind = "link", kids = { node_text(url) }, url = url }
 	end
@@ -339,6 +345,14 @@ if has_lpeg then
 	local address = (alnum + S(".!#$%&'*+/=?^_`{|}~-")) ^ 1
 		* P("@") * alnum * (alnum + S(".-")) ^ 0
 
+	-- A character reference passes through for the browser to decode,
+	-- within CommonMark's lengths. Its shape leaves no room for markup, and
+	-- a name the browser does not know shows as written.
+	local digit, hex = R("09"), R("09", "af", "AF")
+	local reference = P("&") * (R("az", "AZ") * alnum ^ -31
+		+ P("#") * digit * digit ^ -6
+		+ P("#") * S("xX") * hex * hex ^ -5) * P(";")
+
 	local label = P("[") * C((1 - P("]")) ^ (-max_scan)) * P("]")
 	local target = P("(") * space ^ 0 * C(url_char * url_char ^ (-max_scan))
 		* (1 - P(")")) ^ (-max_scan) * P(")")
@@ -349,6 +363,7 @@ if has_lpeg then
 	local inline_grammar = Ct((
 		  (P("`") * C((1 - P("`")) ^ 1) * P("`")) / node_code
 		+ (P("\\") * C(punctuation)) / node_text
+		+ C(reference) / node_reference
 		+ (P("<") * C(uri) * P(">")) / node_autolink
 		+ (P("<") * C(address) * P(">")) / node_mail
 		+ (P("[!") * label * target * P("]") * target) / node_image