SimpleXLSX is software for parsing and retrieving data from Excel XLSx files. Starting in 1.0.12 and ending in 1.1.13, when calling the extended toHTMLEx method, it is possible to execute arbitrary JavaScript code. This vulnerability is fixed in 1.1.13.
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.