added a screening page for external links. removed forced target = _blank on external links for UX consideration

used http://www.deviantart.com/users/outgoing?http://www.nodebb.org/ for
inspiration

app.js

@@ -70,7 +70,7 @@ if (!nconf.get('setup') && nconf.get('base_url')) {
 			config['ROOT_DIRECTORY'] = __dirname;
 
 			templates.init([
-				'header', 'footer', 'logout', 'admin/header', 'admin/footer', 'admin/index',
+				'header', 'footer', 'logout', 'outgoing', 'admin/header', 'admin/footer', 'admin/index',
 				'emails/reset', 'emails/reset_plaintext', 'emails/email_confirm', 'emails/email_confirm_plaintext',
 				'emails/header', 'emails/footer', 'install/header', 'install/footer', 'install/redis',
 

public/templates/outgoing.tpl

@@ -0,0 +1,11 @@
+<div class="hero-unit">
+	<h2 class="form-signin-heading">Now Leaving NodeBB</h2>
+	<p>
+		You are now leaving NodeBB.
+	</p>
+	<br />
+	<p>
+		<button class="btn btn-large" type="button" onclick="window.location='{url}'">Continue to {url}</button>
+		<button class="btn btn-large btn-inverse" type="button" onclick="history.go(-1); window.location='{home}'">Return to NodeBB</button>
+	</p>
+</div>

src/postTools.js

@@ -148,9 +148,19 @@ var	RDB = require('./redis.js'),
 
 		if (md.length > 0) {
 			var	parsedContentDOM = cheerio.load(marked(md));
-			parsedContentDOM('a').attr('rel', 'nofollow').attr('target', '_blank');
+			parsedContentDOM('a').attr('rel', 'nofollow');
+
+			var href = parsedContentDOM('a').attr('href'),
+				domain = global.nconf.get('url');
+
+			if (href && !href.match(domain)) {
+				parsedContentDOM('a').attr('href', domain + 'outgoing?' + href);
+			}
+
 			html = parsedContentDOM.html();
-		} else html = '<p></p>';
+		} else {
+			html = '<p></p>';
+		}
 
 		return html;
 	}

src/webserver.js

@@ -278,6 +278,20 @@ var express = require('express'),
 			});
 		});
 
+		app.get('/outgoing', function(req, res) {
+			var url = req.url.split('?');
+
+			if (url[1]) {
+				res.send(app.build_header(res) + templates['outgoing'].parse({
+					url: url[1],
+					home: global.nconf.get('url')
+				}) + templates['footer']);
+			} else {
+				res.status(404);
+				res.redirect(global.nconf.get('relative_path') + '/404');
+			}
+		});
+
 	});
 	
 	// These functions are called via ajax once the initial page is loaded to populate templates with data