Fix another clusterfuzz identified issue (#15096) (#15114)

zeripath · techknowlogick · web-flow · commit 6198403fbc4e · 2021-03-22T16:27:21.000-04:00
Backport #15096 Signed-off-by: Andrew Thornton <art27@cantab.net> Co-authored-by: techknowlogick <techknowlogick@gitea.io>
diff --git a/modules/markup/html.go b/modules/markup/html.go
@@ -312,7 +312,7 @@ func (ctx *postProcessCtx) postProcess(rawHTML []byte) ([]byte, error) {
 	_, _ = res.WriteString("<html><body>")
 
 	// Strip out nuls - they're always invalid
-	_, _ = nulCleaner.WriteString(res, string(tagCleaner.ReplaceAll(rawHTML, []byte("&lt;$1"))))
+	_, _ = res.Write(tagCleaner.ReplaceAll([]byte(nulCleaner.Replace(string(rawHTML))), []byte("&lt;$1")))
 
 	// close the tags
 	_, _ = res.WriteString("</body></html>")
