Hi Maki,
Thanks for the info - please can you provide the other details requested as well?
I believe this is likely due to either an incompatibility or bug with the version of Slimjet you're using. The version you're using is the 4th oldest release, and is using an outdated version of Chromium as it's base.
Please can you update to the latest version of Slimjet and confirm if you still get the error? The latest version is 17.0.2, based on Chromium 63.
If you're still getting an XSS issue, it's likely our forum software does not currently support SlimJet. As this browser alters the webpage itself, it's possible that the way it is doing this is creating a broken code issue which the XSS Auditor then picks up as an XSS error.