diff --git a/4.1-Extensions.md b/4.1-Extensions.md
index 927a6a0..cb529b2 100644
--- a/4.1-Extensions.md
+++ b/4.1-Extensions.md
@@ -9,7 +9,7 @@ This list covers privacy and security related extensions only. While we believe
 :exclamation: **CSP**: When multiple extensions use CSP injection to modify headers, only one wins and predicting the winner is like [rolling a dice](https://github.com/ghacksuserjs/ghacks-user.js/issues/265#issuecomment-393935989). Some CSP items (this is not an exhaustive list) to be aware of are highlighted below.
 
 * [uBlock Origin](https://addons.mozilla.org/firefox/addon/ublock-origin/) <sup>✔ [Privacy](https://github.com/gorhill/uBlock/wiki/Privacy-policy)</sup> | [GitHub](https://github.com/gorhill/uBlock)
-  * :exclamation: **CSP**: Uncheck `Dashboard > Settings > Block remote fonts`. Font rules use CSP. Use Request Control instead.
+  * :exclamation: **CSP**: Uncheck `Dashboard > Settings > Block remote fonts`. Font rules use CSP, use Request Control instead. [Other CSP issues](https://github.com/ghacksuserjs/ghacks-user.js/issues/664#issuecomment-472596147) include filter lists that use `$csp=` (and there are lot of them)
 * [Privacy Badger](https://addons.mozilla.org/firefox/addon/privacy-badger17/) <sup>✔ [Privacy](https://addons.mozilla.org/firefox/addon/privacy-badger17/privacy/)</sup> | [GitHub](https://github.com/EFForg/privacybadger)
    * Uses [heuristics](https://www.eff.org/privacybadger/faq#How-does-Privacy-Badger-work) to learn and to build local blocking lists. Your mileage will depend on what other blocking extensions you use and their configurations, but it [certainly can't hurt](https://www.eff.org/privacybadger/faq#Is-Privacy-Badger-compatible-with-other-extensions,-including-other-adblockers).
 * [uMatrix](https://addons.mozilla.org/firefox/addon/umatrix/) <sup>✔ [Privacy](https://github.com/gorhill/uMatrix/wiki/Privacy-policy)</sup> | [GitHub](https://github.com/gorhill/uMatrix)