HRConvert2: Missing Sanitization enables Unauthenticated Remote Command Execution

HRConvert2 is a self-hosted, drag-and-drop & nosql file conversion server & share tool. Prior to 3.3.8, the sanitizeString() function in convertCore.php is missing backtick (`) and tab (\t) from its strip list. User input then reaches shell_exec(), where the shell interprets these characters and commands within filenames execute. This vulnerability is fixed in 3.3.8.