added slice bounds check

inline_test.go

@@ -613,6 +613,27 @@ what happens here
 </li>
 </ol>
 </div>
+`,
+
+		`This is a footnote[^1]^[and this is an inline footnote]
+
+[^1]: the footnote text.
+
+    may be multiple paragraphs.
+`,
+		`<p>This is a footnote<sup class="footnote-ref" id="fnref:1"><a rel="footnote" href="#fn:1">1</a></sup><sup class="footnote-ref" id="fnref:and-this-is-an-i"><a rel="footnote" href="#fn:and-this-is-an-i">2</a></sup></p>
+<div class="footnotes">
+
+<hr />
+
+<ol>
+<li id="fn:1"><p>the footnote text.</p>
+
+<p>may be multiple paragraphs.</p>
+</li>
+<li id="fn:and-this-is-an-i">and this is an inline footnote</li>
+</ol>
+</div>
 `,
 	}
 

markdown.go

@@ -589,12 +589,12 @@ func scanLinkRef(p *parser, data []byte, i int) (linkOffset, linkEnd, titleOffse
 // extracted text that was shifted over one tab. It will need to be rendered at
 // the end of the document.
 func scanFootnote(p *parser, data []byte, i, indentSize int) (blockStart, blockEnd int, contents []byte, hasBlock bool) {
-	if i == 0 {
+	if i == 0 || len(data) == 0 {
 		return
 	}
 
 	// skip leading whitespace on first line
-	for data[i] == ' ' {
+	for i < len(data) && data[i] == ' ' {
 		i++
 	}