With PowerCHM you can create your CHM files automatically from Html Files (including .htm, .html and .mht), Text Files (.txt), Microsoft Word Documents (.doc) and Adobe Acrobat Document (.pdf).
The vulnerability is caused due to a boundary error when processing overly long filenames. This can be exploited to cause a stack-based buffer overflow by e.g. tricking a user into opening an HTML Help Project (".HHP") file having an overly long "[FILES]" entry or into clicking an overly long link included in an imported HTML file. Successful exploitation may allow execution of arbitrary code.