An issue was discovered in in TortoiseSVN 1.12.1. The Tsvncmd: URI handler allows a customised diff operation on Excel workbooks which could be used to open remote workbooks without protection from macro security settings to execute arbitrary code. A tsvncmd:command:diff?path:file1?path2:file2 URI will execute a customised diff on file1 and file2 based on the file extension. For xls files it will execute the script diff-xls.js using wscript which will open the two files for analysis without any macro security warning. An attacker can exploit this by putting a macro virus in a network drive and force the victim to open the workbooks and execute the macro inside.