True, but it is a known vector the delivery of malware, at least on Windows: https://blog.checkpoint.com/2015/05/12/the-microsoft-help-file-chm-may-enslave-you/
Also, there seems to be no default program for opening .CHM files on Trisquel 7. I decided to take the risk and open one, but the system tells me no program is available to open such a file.
