escape regex chars

lib/find.js

@@ -9,7 +9,8 @@ exports.selectArticle = selectArticle;
 
 function narrowDown(articles, terms, deep, apropos) {
   var reSearchTerms = terms.map(function mapRE(term) {
-    return new RegExp(term, 'i');
+    // escape invalid regex characters in the search terms before making a new regex
+    return new RegExp(term.replace(/[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|]/g, '\\$&'), 'i');
   });
 
   var filtered = articles.filter(function filterOutCategoryPages(article) {