According to your screenshot your site has been scanned by some software (finding vulnerabilities). You can ignore them. Or you can even disable them by setting "CommonSettings.Log404Errors" to "False"
These are done by BOTS. They try to access some non-existence URLs, and since they are non-existence, nopCommerce throw errors.
You can view the log details, get the IP, and check online for the origin of the IP. Sometimes it's search engine bots like BING or Google, sometimes it's spam bots.