The readme.html file in your WordPress installation contains information about which version you have installed and it can help hackers better attack your website knowing this.
There are other methods to determine which version of WordPress you are using, but you can easily eliminate this method. There is no practical use for the readme.html file, you can delete it with ease.
If you use the Pro version you can use the “Remove Unwanted Files” fix to easily remove the readme.html and many other typical files you want to remove.
If you use the free version you will have to manually log in to your website via FTP to delete the file or to check if your website service provider has a web interface to access and modify your website files.
