Remove support for [iframe] BBCode

- It was a huge gaping security hole, and now HTML Purify will remove the src attribute of all non-allowed sources anyway.

doc/BBCode.md

@@ -502,10 +502,6 @@ You can embed video, audio and more in a message.
   <td>[embed]URL[/embed]</td>
   <td>Embed OEmbed rich content.</td>
 </tr>
-<tr>
-  <td>[iframe]URL[/iframe]</td>
-  <td>General embed, iframe size is limited by the theme size for video players.</td>
-</tr>
 <tr>
   <td>[url]*url*[/url]</td>
   <td>If *url* supports oembed or opengraph specifications the embedded object will be shown (eg, documents from scribd).

doc/de/BBCode.md

@@ -482,10 +482,6 @@ Du kannst Videos, Musikdateien und weitere Dinge in Beiträgen einbinden.
   <td>[embed]URL[/embed]</td>
   <td>OEmbed rich content einbetten.</td>
 </tr>
-<tr>
-  <td>[iframe]URL[/iframe]</td>
-  <td>General embed, iframe size is limited by the theme size for video players.</td>
-</tr>
 <tr>
   <td>[url]*url*[/url]</td>
   <td>Wenn *url* die OEmbed- oder Opengraph-Spezifikationen unterst&uuml;tzt, wird das Objekt eingebettet (z.B. Dokumente von scribd).

src/Content/Text/BBCode.php

@@ -1622,11 +1622,8 @@ class BBCode
 						'<a href="$1" target="_blank" rel="noopener noreferrer">$1</a>', $text);
 				}
 
-				if ($try_oembed) {
-					$text = preg_replace("/\[iframe\](.*?)\[\/iframe\]/ism", '<iframe src="$1" width="' . $a->videowidth . '" height="' . $a->videoheight . '"><a href="$1">$1</a></iframe>', $text);
-				} else {
-					$text = preg_replace("/\[iframe\](.*?)\[\/iframe\]/ism", '<a href="$1">$1</a>', $text);
-				}
+				// Backward compatibility, [iframe] support has been removed in version 2020.12
+				$text = preg_replace("/\[iframe\](.*?)\[\/iframe\]/ism", '<a href="$1">$1</a>', $text);
 
 				// Youtube extensions
 				if ($try_oembed) {

src/Content/Text/HTML.php

@@ -290,7 +290,8 @@ class HTML
 
 			self::tagToBBCode($doc, 'video', ['src' => '/(.+)/'], '[video]$1', '[/video]', true);
 			self::tagToBBCode($doc, 'audio', ['src' => '/(.+)/'], '[audio]$1', '[/audio]', true);
-			self::tagToBBCode($doc, 'iframe', ['src' => '/(.+)/'], '[iframe]$1', '[/iframe]', true);
+			// Backward compatibility, [iframe] support has been removed in version 2020.12
+			self::tagToBBCode($doc, 'iframe', ['src' => '/(.+)/'], '[url]$1', '[/url]', true);
 
 			self::tagToBBCode($doc, 'key', [], '[code]', '[/code]');
 			self::tagToBBCode($doc, 'code', [], '[code]', '[/code]');
@@ -630,6 +631,7 @@ class HTML
 			self::tagToBBCode($doc, 'img', ['src' => '/(.+)/'], ' ', ' ');
 		}
 
+		// Backward compatibility, [iframe] support has been removed in version 2020.12
 		self::tagToBBCode($doc, 'iframe', ['src' => '/(.+)/'], ' $1 ', '');
 
 		$message = $doc->saveHTML();