Index: _source/plugins/htmldataprocessor/plugin.js
===================================================================
--- _source/plugins/htmldataprocessor/plugin.js	(revision 5878)
+++ _source/plugins/htmldataprocessor/plugin.js	(revision )
@@ -317,6 +317,11 @@
 		return html.replace( protectSelfClosingRegex, '<cke:$1$2></cke:$1>' );
 	}
 
+	function protectPreFormatted( html )
+	{
+		return html.replace( /(<pre\b[^>]*>)(\r\n|\n)/g, '$1$2$2' );
+	}
+
 	function protectRealComments( html )
 	{
 		return html.replace( /<!--(?!{cke_protected})[\s\S]+?-->/g, function( match )
@@ -437,6 +442,10 @@
 			// protecting them into open-close. (#3591)
 			data = protectSelfClosingElements( data );
 
+			// Compensate one leading line break after <pre> open as browsers
+			// eat it up. (#5789)
+			data = protectPreFormatted( data );
+
 			// Call the browser to help us fixing a possibly invalid HTML
 			// structure.
 			var div = new CKEDITOR.dom.element( 'div' );
Index: _source/plugins/htmlwriter/plugin.js
===================================================================
--- _source/plugins/htmlwriter/plugin.js	(revision 5336)
+++ _source/plugins/htmlwriter/plugin.js	(revision )
@@ -63,6 +63,8 @@
 
 		this._.indent = false;
 		this._.indentation = '';
+		// Indicate preformatted block context status. (#5789)
+		this._.inPre = 0;
 		this._.rules = {};
 
 		var dtd = CKEDITOR.dtd;
@@ -158,6 +160,7 @@
 
 			if ( rules && rules.breakAfterOpen )
 				this.lineBreak();
+			tagName == 'pre' && ( this._.inPre = 1 );
 		},
 
 		/**
@@ -206,6 +209,7 @@
 			}
 
 			this._.output.push( '</', tagName, '>' );
+			tagName == 'pre' && ( this._.inPre = 0 );
 
 			if ( rules && rules.breakAfterClose )
 				this.lineBreak();
@@ -223,7 +227,7 @@
 			if ( this._.indent )
 			{
 				this.indentation();
-				text = CKEDITOR.tools.ltrim( text );
+				!this._.inPre  && ( text = CKEDITOR.tools.ltrim( text ) );
 			}
 
 			this._.output.push( text );
@@ -252,7 +256,7 @@
 		 */
 		lineBreak : function()
 		{
-			if ( this._.output.length > 0 )
+			if ( !this._.inPre && this._.output.length > 0 )
 				this._.output.push( this.lineBreakChars );
 			this._.indent = true;
 		},
@@ -267,7 +271,8 @@
 		 */
 		indentation : function()
 		{
+			if( !this._.inPre )
-			this._.output.push( this._.indentation );
+				this._.output.push( this._.indentation );
 			this._.indent = false;
 		},