diff --git a/system/core/Security.php b/system/core/Security.php
index 4a69daa..b9160a2 100644
--- a/system/core/Security.php
+++ b/system/core/Security.php
@@ -371,11 +371,17 @@
 		 *
 		 * Note: Use rawurldecode() so it does not remove plus signs
 		 */
-		do
+		if (stripos($str, '%') !== false)
 		{
-			$str = rawurldecode($str);
+			do
+			{
+				$oldstr = $str;
+				$str = rawurldecode($str);
+				$str = preg_replace_callback('#%(?:\s*[0-9a-f]){2,}#i', array($this, '_urldecodespaces'), $str);
+			}
+			while ($oldstr !== $str);
+			unset($oldstr);
 		}
-		while (preg_match('/%[0-9a-f]{2,}/i', $str));
 
 		/*
 		 * Convert character entities to ASCII
@@ -466,7 +472,7 @@
 
 			if (preg_match('/<a/i', $str))
 			{
-				$str = preg_replace_callback('#<a[^a-z0-9>]+([^>]*?)(?:>|$)#si', array($this, '_js_link_removal'), $str);
+				$str = preg_replace_callback('#<a(?:rea)?[^a-z0-9>]+([^>]*?)(?:>|$)#si', array($this, '_js_link_removal'), $str);
 			}
 
 			if (preg_match('/<img/i', $str))
@@ -775,6 +781,24 @@
 	// ----------------------------------------------------------------
 
 	/**
+	 * URL-decode taking spaces into account
+	 *
+	 * @see		https://github.com/bcit-ci/CodeIgniter/issues/4877
+	 * @param	array	$matches
+	 * @return	string
+	 */
+	protected function _urldecodespaces($matches)
+	{
+		$input    = $matches[0];
+		$nospaces = preg_replace('#\s+#', '', $input);
+		return ($nospaces === $input)
+			? $input
+			: rawurldecode($nospaces);
+	}
+
+	// ----------------------------------------------------------------
+
+	/**
 	 * Compact Exploded Words
 	 *
 	 * Callback method for xss_clean() to remove whitespace from
@@ -803,7 +827,7 @@
 	protected function _sanitize_naughty_html($matches)
 	{
 		static $naughty_tags    = array(
-			'alert', 'prompt', 'confirm', 'applet', 'audio', 'basefont', 'base', 'behavior', 'bgsound',
+			'alert', 'area', 'prompt', 'confirm', 'applet', 'audio', 'basefont', 'base', 'behavior', 'bgsound',
 			'blink', 'body', 'embed', 'expression', 'form', 'frameset', 'frame', 'head', 'html', 'ilayer',
 			'iframe', 'input', 'button', 'select', 'isindex', 'layer', 'link', 'meta', 'keygen', 'object',
 			'plaintext', 'style', 'script', 'textarea', 'title', 'math', 'video', 'svg', 'xml', 'xss'