diff --git a/boards/mdx_neboard.py b/boards/mdx_neboard.py
--- a/boards/mdx_neboard.py
+++ b/boards/mdx_neboard.py
@@ -10,7 +10,7 @@ import boards
 AUTOLINK_PATTERN = r'(https?://\S+)'
 QUOTE_PATTERN = r'^(?<!>)(>[^>].+)$'
 REFLINK_PATTERN = r'((>>)(\d+))'
-SPOILER_PATTERN = r'%%(.+)%%'
+SPOILER_PATTERN = r'%%([^(%%)]+)%%'
 COMMENT_PATTERN = r'^(//(.+))'
 STRIKETHROUGH_PATTERN = r'~(.+)~'