An issue was discovered 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.