diff --git a/apply-css/README.md b/apply-css/README.md
index 0ac3193..c027dde 100644
--- a/apply-css/README.md
+++ b/apply-css/README.md
@@ -1,5 +1,7 @@
 # apply-css
 
+**This add-on injects CSS into web pages. The `addons.mozilla.org` domain disallows this operation, so this add-on will not work properly when it's run on pages in the `addons.mozilla.org` domain.**
+
 ## What it does
 
 This extension includes:
diff --git a/beastify/README.md b/beastify/README.md
index 54c9864..941189a 100644
--- a/beastify/README.md
+++ b/beastify/README.md
@@ -1,5 +1,7 @@
 # beastify
 
+**This add-on injects JavaScript into web pages. The `addons.mozilla.org` domain disallows this operation, so this add-on will not work properly when it's run on pages in the `addons.mozilla.org` domain.**
+
 ## What it does ##
 
 The extension includes:
diff --git a/borderify/README.md b/borderify/README.md
index ea3b498..1624883 100644
--- a/borderify/README.md
+++ b/borderify/README.md
@@ -1,5 +1,7 @@
 # borderify
 
+**This add-on injects JavaScript into web pages. The `addons.mozilla.org` domain disallows this operation, so this add-on will not work properly when it's run on pages in the `addons.mozilla.org` domain.**
+
 ## What it does
 
 This extension just includes:
diff --git a/context-menu-demo/README.md b/context-menu-demo/README.md
index 65e0426..c8b301c 100644
--- a/context-menu-demo/README.md
+++ b/context-menu-demo/README.md
@@ -2,6 +2,8 @@
 
 A demo of the [contextMenus API](https://developer.mozilla.org/en-US/Add-ons/WebExtensions/API/contextMenus/).
 
+**This add-on injects JavaScript into web pages. The `addons.mozilla.org` domain disallows this operation, so this add-on will not work properly when it's run on pages in the `addons.mozilla.org` domain.**
+
 ## What it does
 
 This add-on adds several items to the browser's context menu:
diff --git a/cookie-bg-picker/README.md b/cookie-bg-picker/README.md
index 5ff23e5..598f83e 100644
--- a/cookie-bg-picker/README.md
+++ b/cookie-bg-picker/README.md
@@ -5,6 +5,8 @@ The WebExtension also uses cookies to save preferences for each site you customi
 
 Works in Firefox 47+, and will also work as a Chrome extension, out of the box.
 
+**This add-on injects JavaScript into web pages. The `addons.mozilla.org` domain disallows this operation, so this add-on will not work properly when it's run on pages in the `addons.mozilla.org` domain.**
+
 ## What it does
 
 This extension includes:
@@ -33,4 +35,4 @@ Cookie BG Picker uses the WebExtension:
 ## Acknowledgements
 
 * WebExtension icon courtesy of [icons8.com](http://icons8.com).
-* Transparent background images taken from [Transparent Textures](https://www.transparenttextures.com/).
\ No newline at end of file
+* Transparent background images taken from [Transparent Textures](https://www.transparenttextures.com/).
diff --git a/emoji-substitution/README.md b/emoji-substitution/README.md
index 7ccc621..e29b7f2 100644
--- a/emoji-substitution/README.md
+++ b/emoji-substitution/README.md
@@ -1,5 +1,7 @@
 # Emoji Substitution
 
+**This add-on injects JavaScript into web pages. The `addons.mozilla.org` domain disallows this operation, so this add-on will not work properly when it's run on pages in the `addons.mozilla.org` domain.**
+
 ## What it does
 
 Replaces words that describe an emoji with the emoji itself. This runs as a content script and scans web pages, looking for text that can be replaced with emoji. As an example, after installing visit https://mozilla.org and notice that the text "firefox" should change.
diff --git a/notify-link-clicks-i18n/README.md b/notify-link-clicks-i18n/README.md
index 26602f1..b1a86d9 100644
--- a/notify-link-clicks-i18n/README.md
+++ b/notify-link-clicks-i18n/README.md
@@ -1,5 +1,7 @@
 # notify-link-clicks-i18n
 
+**This add-on injects JavaScript into web pages. The `addons.mozilla.org` domain disallows this operation, so this add-on will not work properly when it's run on pages in the `addons.mozilla.org` domain.**
+
 ## What it does
 
 This extension includes:
diff --git a/selection-to-clipboard/README.md b/selection-to-clipboard/README.md
index b9f5912..5169b7b 100644
--- a/selection-to-clipboard/README.md
+++ b/selection-to-clipboard/README.md
@@ -1,5 +1,7 @@
 # selection-to-clipboard
 
+**This add-on injects JavaScript into web pages. The `addons.mozilla.org` domain disallows this operation, so this add-on will not work properly when it's run on pages in the `addons.mozilla.org` domain.**
+
 ## What it does
 
 This extension includes: