diff --git a/packages/app-cli/tests/support/plugins/content_script/src/markdownItTestPlugin.ts b/packages/app-cli/tests/support/plugins/content_script/src/markdownItTestPlugin.ts
index d781ae21f9..de880a1e6b 100644
--- a/packages/app-cli/tests/support/plugins/content_script/src/markdownItTestPlugin.ts
+++ b/packages/app-cli/tests/support/plugins/content_script/src/markdownItTestPlugin.ts
@@ -13,13 +13,6 @@ export default function(context) {
 				const token = tokens[idx];
 				if (token.info !== 'justtesting') return defaultRender(tokens, idx, options, env, self);
 
-				const postMessageWithResponseTest = `
-					webviewApi.postMessage('${contentScriptId}', 'justtesting').then(function(response) {
-						console.info('Got response in content script: ' + response);
-					});
-					return false;
-				`;
-
 				// Rich text editor support:
 				// The joplin-editable and joplin-source CSS classes mark the generated div
 				// as a region that needs special processing when converting back to markdown.
@@ -38,14 +31,23 @@ export default function(context) {
 						${richTextEditorMetadata}
 
 						<p>JUST TESTING: <pre>${markdownIt.utils.escapeHtml(leftPad(token.content.trim(), 10, 'x'))}</pre></p>
-						<p><a href="#" onclick="${postMessageWithResponseTest.replace(/\n/g, ' ')}">Click to post a message "justtesting" to plugin and check the response in the console</a></p>
+						<p>
+							<a
+								href="#"
+								data-content-script-id="${markdownIt.utils.escapeHtml(contentScriptId)}"
+								class="post-message-link"
+							>
+								Click to post a message "justtesting" to plugin and check the response in the console
+							</a>
+						</p>
 					</div>
 				`;
 			};
 		},
 		assets: function() {
 			return [
-				{ name: 'markdownItTestPlugin.css' }
+				{ name: 'markdownItTestPlugin.css' },
+				{ name: 'markdownItTestPluginRuntime.js' },
 			];
 		},
 	}
diff --git a/packages/app-cli/tests/support/plugins/content_script/src/markdownItTestPluginRuntime.js b/packages/app-cli/tests/support/plugins/content_script/src/markdownItTestPluginRuntime.js
new file mode 100644
index 0000000000..b3c0150ad0
--- /dev/null
+++ b/packages/app-cli/tests/support/plugins/content_script/src/markdownItTestPluginRuntime.js
@@ -0,0 +1,14 @@
+const addClickHandlers = () => {
+	const postMessageLinks = document.querySelectorAll('.post-message-link');
+	for (const link of postMessageLinks) {
+		const contentScriptId = link.getAttribute('data-content-script-id');
+		link.onclick = async () => {
+			const response = await webviewApi.postMessage(contentScriptId, 'justtesting');
+			link.textContent = 'Got response in content script: ' + response;
+		};
+	}
+};
+
+document.addEventListener('joplin-noteDidUpdate', () => {
+	addClickHandlers();
+});
diff --git a/packages/app-desktop/gui/NoteEditor/NoteBody/TinyMCE/TinyMCE.tsx b/packages/app-desktop/gui/NoteEditor/NoteBody/TinyMCE/TinyMCE.tsx
index 01ed279071..0dc1265dd2 100644
--- a/packages/app-desktop/gui/NoteEditor/NoteBody/TinyMCE/TinyMCE.tsx
+++ b/packages/app-desktop/gui/NoteEditor/NoteBody/TinyMCE/TinyMCE.tsx
@@ -43,6 +43,7 @@ import useKeyboardRefocusHandler from './utils/useKeyboardRefocusHandler';
 import useDocument from '../../../hooks/useDocument';
 import useEditDialog from './utils/useEditDialog';
 import useEditDialogEventListeners from './utils/useEditDialogEventListeners';
+import Setting from '@joplin/lib/models/Setting';
 import useTextPatternsLookup from './utils/useTextPatternsLookup';
 
 const logger = Logger.create('TinyMCE');
@@ -728,6 +729,25 @@ const TinyMCE = (props: NoteBodyEditorProps, ref: any) => {
 				language_url: ['en_US', 'en_GB'].includes(language) ? undefined : `${bridge().vendorDir()}/lib/tinymce/langs/${language}`,
 				toolbar: toolbar.join(' '),
 				localization_function: _,
+				// See https://www.tiny.cloud/docs/tinymce/latest/tinymce-and-csp/#content_security_policy
+				content_security_policy: Setting.value('featureFlag.richText.useStrictContentSecurityPolicy') ? [
+					// Media: *: Allow users to include images and videos from the internet (e.g. ![](http://example.com/image.png)).
+					// Media: blob: Allow loading images/videos/audio from blob URLs. The Rich Text Editor
+					//      replaces certain base64 URLs with blob URLs.
+					// Media: data: Allow loading images and other media from data: URLs
+					'default-src \'self\'',
+					'img-src \'self\' blob: data: *', // Images
+					'media-src \'self\' blob: data: *', // Audio and video players
+
+					// Disallow certain unused features
+					'child-src \'none\'', // Should not contain sub-frames
+					'object-src \'none\'', // Objects can be used for script injection
+					'form-action \'none\'', // No submitting forms
+
+					// Styles: unsafe-inline: TinyMCE uses inline style="" styles.
+					// Styles: *: Allow users to include styles from the internet (e.g. <style src="https://example.com/style.css">)
+					'style-src \'self\' \'unsafe-inline\' * data:',
+				].join(' ; ') : undefined,
 				contextmenu: false,
 				browser_spellcheck: true,
 
diff --git a/packages/app-desktop/gui/NoteEditor/NoteBody/TinyMCE/utils/useWebViewApi.ts b/packages/app-desktop/gui/NoteEditor/NoteBody/TinyMCE/utils/useWebViewApi.ts
index 8ea5dd5cf9..6d61aef030 100644
--- a/packages/app-desktop/gui/NoteEditor/NoteBody/TinyMCE/utils/useWebViewApi.ts
+++ b/packages/app-desktop/gui/NoteEditor/NoteBody/TinyMCE/utils/useWebViewApi.ts
@@ -2,72 +2,37 @@ import PluginService from '@joplin/lib/services/plugins/PluginService';
 import { useEffect } from 'react';
 import { Editor } from 'tinymce';
 
-const useWebViewApi = (editor: Editor, window: Window) => {
+interface WebViewApi {
+	postMessage: (contentScriptId: string, message: unknown)=> Promise<unknown>;
+}
+
+interface ExtendedWindow extends Window {
+	webviewApi: WebViewApi;
+}
+
+const useWebViewApi = (editor: Editor, containerWindow: Window) => {
 	useEffect(() => {
 		if (!editor) return ()=>{};
-		if (!window) return ()=>{};
+		if (!containerWindow) return ()=>{};
 
-		const scriptElement = window.document.createElement('script');
-		const channelId = `plugin-post-message-${Math.random()}`;
-		scriptElement.appendChild(window.document.createTextNode(`
-			window.webviewApi = {
-				postMessage: (contentScriptId, message) => {
-					const channelId = ${JSON.stringify(channelId)};
-					const messageId = Math.random();
-					window.parent.postMessage({
-						channelId,
-						messageId,
-						contentScriptId,
-						message,
-					}, '*');
-
-					const waitForResponse = async () => {
-						while (true) {
-							const messageEvent = await new Promise(resolve => {
-								window.addEventListener('message', event => {
-									resolve(event);
-								}, {once: true});
-							});
-	
-							if (messageEvent.source !== window.parent || messageEvent.data.messageId !== messageId) {
-								continue;
-							}
-	
-							const data = messageEvent.data;
-							return data.response;
-						}
-					};
-
-					return waitForResponse();
-				},
-			};
-		`));
-		const editorWindow = editor.getWin();
-		editorWindow.document.head.appendChild(scriptElement);
-
-		const onMessageHandler = async (event: MessageEvent) => {
-			if (event.source !== editorWindow || event.data.channelId !== channelId) {
-				return;
-			}
-
-			const contentScriptId = event.data.contentScriptId;
-			const pluginService = PluginService.instance();
-			const plugin = pluginService.pluginById(
-				pluginService.pluginIdByContentScriptId(contentScriptId),
-			);
-			const result = await plugin.emitContentScriptMessage(contentScriptId, event.data.message);
-			editorWindow.postMessage({
-				messageId: event.data.messageId,
-				response: result,
-			}, '*');
+		const editorWindow = editor.getWin() as ExtendedWindow;
+		const webviewApi: WebViewApi = {
+			postMessage: async (contentScriptId: string, message: unknown) => {
+				const pluginService = PluginService.instance();
+				const plugin = pluginService.pluginById(
+					pluginService.pluginIdByContentScriptId(contentScriptId),
+				);
+				return await plugin.emitContentScriptMessage(contentScriptId, message);
+			},
 		};
-		window.addEventListener('message', onMessageHandler);
+		editorWindow.webviewApi = webviewApi;
 
 		return () => {
-			window.removeEventListener('message', onMessageHandler);
-			scriptElement.remove();
+			if (editorWindow.webviewApi === webviewApi) {
+				editorWindow.webviewApi = undefined;
+			}
 		};
-	}, [editor, window]);
+	}, [editor, containerWindow]);
 };
 
 export default useWebViewApi;
diff --git a/packages/app-desktop/gui/NoteEditor/NoteEditor.tsx b/packages/app-desktop/gui/NoteEditor/NoteEditor.tsx
index c139a591e4..5b2cb3d3fa 100644
--- a/packages/app-desktop/gui/NoteEditor/NoteEditor.tsx
+++ b/packages/app-desktop/gui/NoteEditor/NoteEditor.tsx
@@ -163,8 +163,7 @@ function NoteEditorContent(props: NoteEditorProps) {
 		scrollbarSize: props.scrollbarSize,
 	});
 
-	// eslint-disable-next-line @typescript-eslint/no-explicit-any -- Old code before rule was applied
-	const allAssets = useCallback(async (markupLanguage: number, options: AllAssetsOptions = null): Promise<any[]> => {
+	const allAssets = useCallback(async (markupLanguage: number, options: AllAssetsOptions = null) => {
 		options = {
 			contentMaxWidthTarget: '',
 			...options,
@@ -172,7 +171,7 @@ function NoteEditorContent(props: NoteEditorProps) {
 
 		const theme = themeStyle(options.themeId ? options.themeId : props.themeId);
 
-		const markupToHtml = markupLanguageUtils.newMarkupToHtml({}, {
+		const markupToHtml = markupLanguageUtils.newMarkupToHtml(props.plugins, {
 			resourceBaseUrl: `joplin-content://note-viewer/${Setting.value('resourceDir')}/`,
 			customCss: props.customCss,
 		});
@@ -183,7 +182,7 @@ function NoteEditorContent(props: NoteEditorProps) {
 			scrollbarSize: props.scrollbarSize,
 			whiteBackgroundNoteRendering: options.whiteBackgroundNoteRendering,
 		});
-	}, [props.themeId, props.scrollbarSize, props.customCss, props.contentMaxWidth]);
+	}, [props.plugins, props.themeId, props.scrollbarSize, props.customCss, props.contentMaxWidth]);
 
 	const handleProvisionalFlag = useCallback(() => {
 		if (props.isProvisional) {
diff --git a/packages/app-mobile/pluginAssets/index.js b/packages/app-mobile/pluginAssets/index.js
index c0185d59d3..9d3fda4ccf 100644
--- a/packages/app-mobile/pluginAssets/index.js
+++ b/packages/app-mobile/pluginAssets/index.js
@@ -1,5 +1,5 @@
 module.exports = {
-hash:"cfa07333af79f4db4bc9ca008fb257f8", files: {
+hash:"6950f3929f5177b0bb2a0c039669810d", files: {
 'highlight.js/atom-one-dark-reasonable.css': { data: require('./highlight.js/atom-one-dark-reasonable.css.base64.js'), mime: 'text/css', encoding: 'base64' },
 'highlight.js/atom-one-light.css': { data: require('./highlight.js/atom-one-light.css.base64.js'), mime: 'text/css', encoding: 'base64' },
 'katex/fonts/KaTeX_AMS-Regular.woff2': { data: require('./katex/fonts/KaTeX_AMS-Regular.woff2.base64.js'), mime: 'application/octet-stream', encoding: 'base64' },
diff --git a/packages/app-mobile/pluginAssets/index.web.js b/packages/app-mobile/pluginAssets/index.web.js
index 6d1b56ef9e..28155600de 100644
--- a/packages/app-mobile/pluginAssets/index.web.js
+++ b/packages/app-mobile/pluginAssets/index.web.js
@@ -1 +1 @@
-module.exports = {"hash":"cfa07333af79f4db4bc9ca008fb257f8","files":["highlight.js/atom-one-dark-reasonable.css","highlight.js/atom-one-light.css","katex/fonts/KaTeX_AMS-Regular.woff2","katex/fonts/KaTeX_Caligraphic-Bold.woff2","katex/fonts/KaTeX_Caligraphic-Regular.woff2","katex/fonts/KaTeX_Fraktur-Bold.woff2","katex/fonts/KaTeX_Fraktur-Regular.woff2","katex/fonts/KaTeX_Main-Bold.woff2","katex/fonts/KaTeX_Main-BoldItalic.woff2","katex/fonts/KaTeX_Main-Italic.woff2","katex/fonts/KaTeX_Main-Regular.woff2","katex/fonts/KaTeX_Math-BoldItalic.woff2","katex/fonts/KaTeX_Math-Italic.woff2","katex/fonts/KaTeX_SansSerif-Bold.woff2","katex/fonts/KaTeX_SansSerif-Italic.woff2","katex/fonts/KaTeX_SansSerif-Regular.woff2","katex/fonts/KaTeX_Script-Regular.woff2","katex/fonts/KaTeX_Size1-Regular.woff2","katex/fonts/KaTeX_Size2-Regular.woff2","katex/fonts/KaTeX_Size3-Regular.woff2","katex/fonts/KaTeX_Size4-Regular.woff2","katex/fonts/KaTeX_Typewriter-Regular.woff2","katex/katex.css","mermaid/mermaid.min.js","mermaid/mermaid_render.js"]}
\ No newline at end of file
+module.exports = {"hash":"6950f3929f5177b0bb2a0c039669810d","files":["highlight.js/atom-one-dark-reasonable.css","highlight.js/atom-one-light.css","katex/fonts/KaTeX_AMS-Regular.woff2","katex/fonts/KaTeX_Caligraphic-Bold.woff2","katex/fonts/KaTeX_Caligraphic-Regular.woff2","katex/fonts/KaTeX_Fraktur-Bold.woff2","katex/fonts/KaTeX_Fraktur-Regular.woff2","katex/fonts/KaTeX_Main-Bold.woff2","katex/fonts/KaTeX_Main-BoldItalic.woff2","katex/fonts/KaTeX_Main-Italic.woff2","katex/fonts/KaTeX_Main-Regular.woff2","katex/fonts/KaTeX_Math-BoldItalic.woff2","katex/fonts/KaTeX_Math-Italic.woff2","katex/fonts/KaTeX_SansSerif-Bold.woff2","katex/fonts/KaTeX_SansSerif-Italic.woff2","katex/fonts/KaTeX_SansSerif-Regular.woff2","katex/fonts/KaTeX_Script-Regular.woff2","katex/fonts/KaTeX_Size1-Regular.woff2","katex/fonts/KaTeX_Size2-Regular.woff2","katex/fonts/KaTeX_Size3-Regular.woff2","katex/fonts/KaTeX_Size4-Regular.woff2","katex/fonts/KaTeX_Typewriter-Regular.woff2","katex/katex.css","mermaid/mermaid.min.js","mermaid/mermaid_render.js"]}
\ No newline at end of file
diff --git a/packages/app-mobile/pluginAssets/mermaid/mermaid_render.js.base64.js b/packages/app-mobile/pluginAssets/mermaid/mermaid_render.js.base64.js
index bf15354150..b941fd812e 100644
--- a/packages/app-mobile/pluginAssets/mermaid/mermaid_render.js.base64.js
+++ b/packages/app-mobile/pluginAssets/mermaid/mermaid_render.js.base64.js
@@ -1 +1 @@
-module.exports = `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`;
\ No newline at end of file
+module.exports = `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`;
\ No newline at end of file
diff --git a/packages/lib/models/settings/builtInMetadata.ts b/packages/lib/models/settings/builtInMetadata.ts
index eb42dd5155..f06bf3e91d 100644
--- a/packages/lib/models/settings/builtInMetadata.ts
+++ b/packages/lib/models/settings/builtInMetadata.ts
@@ -1727,6 +1727,17 @@ const builtInMetadata = (Setting: typeof SettingType) => {
 			isGlobal: true,
 		},
 
+		'featureFlag.richText.useStrictContentSecurityPolicy': {
+			value: true,
+			type: SettingItemType.Bool,
+			public: true,
+			storage: SettingStorage.File,
+			label: () => 'Stronger security controls in the Rich Text Editor',
+			description: () => 'Improves Rich Text Editor security by applying a strict content security policy to the Rich Text Editor\'s content.',
+			section: 'note',
+			isGlobal: true,
+		},
+
 		'sync.allowUnsupportedProviders': {
 			value: -1,
 			type: SettingItemType.Int,
diff --git a/packages/renderer/MdToHtml.ts b/packages/renderer/MdToHtml.ts
index ca048f66e1..b0031ea9da 100644
--- a/packages/renderer/MdToHtml.ts
+++ b/packages/renderer/MdToHtml.ts
@@ -399,9 +399,10 @@ export default class MdToHtml implements MarkupRenderer {
 	public async allAssets(theme: any, noteStyleOptions: NoteStyleOptions = null) {
 		// eslint-disable-next-line @typescript-eslint/no-explicit-any -- Old code before rule was applied
 		const assets: any = {};
-		for (const key in rules) {
+		const allRules = { ...rules, ...this.extraRendererRules_ };
+		for (const key in allRules) {
 			if (!this.pluginEnabled(key)) continue;
-			const rule = rules[key];
+			const rule = allRules[key];
 
 			if (rule.assets) {
 				assets[key] = rule.assets(theme);
diff --git a/packages/renderer/MdToHtml/rules/mermaid.ts b/packages/renderer/MdToHtml/rules/mermaid.ts
index 55b522b289..09714b6188 100644
--- a/packages/renderer/MdToHtml/rules/mermaid.ts
+++ b/packages/renderer/MdToHtml/rules/mermaid.ts
@@ -98,17 +98,6 @@ export default {
 
 const exportGraphButton = (ruleOptions: RuleOptions) => {
 	const theme = ruleOptions.theme;
-	// Clicking on export button manually triggers a right click context menu event
-	const onClickHandler = `
-		const target = arguments[0].target;
-		const button = target.closest("div.mermaid-export-graph");
-		if (!button) return false;
-		const $mermaid_elem = button.nextElementSibling;
-		const rightClickEvent = new PointerEvent("contextmenu", {bubbles: true});
-		rightClickEvent.target = $mermaid_elem;
-		$mermaid_elem.dispatchEvent(rightClickEvent);
-		return false;
-	`.trim();
 	const style = `
 		display: block;	
 		margin-left: auto;
@@ -119,9 +108,10 @@ const exportGraphButton = (ruleOptions: RuleOptions) => {
 		border: ${theme.buttonStyle.border};
 	`.trim();
 
+	// OnClick is handled in the renderer script
 	return `
 		<div class="mermaid-export-graph">
-			<button onclick='${onClickHandler}' style="${style}" alt="Export mermaid graph">${downloadIcon()}</button>
+			<button style="${style}" alt="Export mermaid graph">${downloadIcon()}</button>
 		</div>
 	`;
 };
diff --git a/packages/renderer/MdToHtml/rules/mermaid_render.js b/packages/renderer/MdToHtml/rules/mermaid_render.js
index 7c5b93c573..f8b7f6d14e 100644
--- a/packages/renderer/MdToHtml/rules/mermaid_render.js
+++ b/packages/renderer/MdToHtml/rules/mermaid_render.js
@@ -22,6 +22,20 @@ const isDarkMode = () => {
 	return !!document.querySelector('.mermaid.joplin--mermaid-use-dark-theme');
 };
 
+const initExportButtons = () => {
+	const exportButtons = document.querySelectorAll('.mermaid-export-graph > button');
+	for (const button of exportButtons) {
+		button.onclick = () => {
+			const buttonContainer = button.parentElement;
+			const mermaidElem = buttonContainer.nextElementSibling;
+
+			const rightClickEvent = new PointerEvent('contextmenu', { bubbles: true });
+			rightClickEvent.target = mermaidElem;
+			mermaidElem.dispatchEvent(rightClickEvent);
+		};
+	}
+};
+
 function mermaidInit() {
 	if (mermaidReady()) {
 		const mermaidTargetNodes = document.getElementsByClassName('mermaid');
@@ -46,6 +60,8 @@ function mermaidInit() {
 		for (const element of mermaidTargetNodes) {
 			element.style.width = '100%';
 		}
+
+		initExportButtons();
 	}
 }
 
diff --git a/packages/renderer/assets/mermaid/mermaid_render.js b/packages/renderer/assets/mermaid/mermaid_render.js
index 7c5b93c573..42128aa232 100644
--- a/packages/renderer/assets/mermaid/mermaid_render.js
+++ b/packages/renderer/assets/mermaid/mermaid_render.js
@@ -22,6 +22,20 @@ const isDarkMode = () => {
 	return !!document.querySelector('.mermaid.joplin--mermaid-use-dark-theme');
 };
 
+const initExportButtons = () => {
+	const exportButtons = document.querySelectorAll('.mermaid-export-graph > button');
+	for (const button of exportButtons) {
+		button.onclick = () => {
+			const buttonContainer = button.parentElement;
+			const mermaidElem = buttonContainer.nextElementSibling;
+
+			const rightClickEvent = new PointerEvent('contextmenu', {bubbles: true});
+			rightClickEvent.target = mermaidElem;
+			mermaidElem.dispatchEvent(rightClickEvent);
+		};
+	}
+};
+
 function mermaidInit() {
 	if (mermaidReady()) {
 		const mermaidTargetNodes = document.getElementsByClassName('mermaid');
@@ -46,6 +60,8 @@ function mermaidInit() {
 		for (const element of mermaidTargetNodes) {
 			element.style.width = '100%';
 		}
+
+		initExportButtons();
 	}
 }