diff --git a/client/components/editor/editor-markdown.vue b/client/components/editor/editor-markdown.vue
index baee118d0..606ba625f 100644
--- a/client/components/editor/editor-markdown.vue
+++ b/client/components/editor/editor-markdown.vue
@@ -224,6 +224,7 @@ import mermaid from 'mermaid'
 
 // Helpers
 import katexHelper from './common/katex'
+import spoiler from './markdown/spoiler'
 import tabsetHelper from './markdown/tabset'
 import cmFold from './common/cmFold'
 
@@ -264,6 +265,7 @@ const md = new MarkdownIt({
   .use(mdAttrs, {
     allowedAttributes: ['id', 'class', 'target']
   })
+  .use(spoiler)
   .use(mdDecorate)
   .use(underline)
   .use(mdEmoji)
diff --git a/client/components/editor/markdown/spoiler.js b/client/components/editor/markdown/spoiler.js
new file mode 100644
index 000000000..d742b1798
--- /dev/null
+++ b/client/components/editor/markdown/spoiler.js
@@ -0,0 +1,12 @@
+const container = require('markdown-it-container')
+
+module.exports = md => md.use(container, 'spoiler', {
+  validate: params => /^spoiler(?:\s+.*)?$/.test(params.trim()),
+  render(tokens, idx) {
+    if (tokens[idx].nesting === 1) {
+      const title = tokens[idx].info.trim().slice('spoiler'.length).trim() || 'Spoiler'
+      return `<details class="spoiler"><summary>${md.utils.escapeHtml(title)}</summary>\n`
+    }
+    return '</details>\n'
+  }
+})
diff --git a/server/modules/rendering/markdown-core/renderer.js b/server/modules/rendering/markdown-core/renderer.js
index 5723214e7..fc83c8823 100644
--- a/server/modules/rendering/markdown-core/renderer.js
+++ b/server/modules/rendering/markdown-core/renderer.js
@@ -2,6 +2,7 @@ const md = require('markdown-it')
 const mdAttrs = require('markdown-it-attrs')
 const mdDecorate = require('markdown-it-decorate')
 const _ = require('lodash')
+const spoiler = require('./spoiler')
 const underline = require('./underline')
 
 const quoteStyles = {
@@ -43,6 +44,7 @@ module.exports = {
     mkdown.use(mdAttrs, {
       allowedAttributes: ['id', 'class', 'target']
     })
+    mkdown.use(spoiler)
     mkdown.use(mdDecorate)
 
     for (let child of this.children) {
diff --git a/server/modules/rendering/markdown-core/spoiler.js b/server/modules/rendering/markdown-core/spoiler.js
new file mode 100644
index 000000000..d742b1798
--- /dev/null
+++ b/server/modules/rendering/markdown-core/spoiler.js
@@ -0,0 +1,12 @@
+const container = require('markdown-it-container')
+
+module.exports = md => md.use(container, 'spoiler', {
+  validate: params => /^spoiler(?:\s+.*)?$/.test(params.trim()),
+  render(tokens, idx) {
+    if (tokens[idx].nesting === 1) {
+      const title = tokens[idx].info.trim().slice('spoiler'.length).trim() || 'Spoiler'
+      return `<details class="spoiler"><summary>${md.utils.escapeHtml(title)}</summary>\n`
+    }
+    return '</details>\n'
+  }
+})
diff --git a/server/test/modules/rendering/markdown-core.test.js b/server/test/modules/rendering/markdown-core.test.js
new file mode 100644
index 000000000..4c0c02526
--- /dev/null
+++ b/server/test/modules/rendering/markdown-core.test.js
@@ -0,0 +1,38 @@
+const renderer = require('../../../modules/rendering/markdown-core/renderer')
+
+const render = input => renderer.render.call({
+  input,
+  children: [],
+  config: {
+    allowHTML: true,
+    linebreaks: true,
+    linkify: true,
+    typographer: false,
+    quotes: 'English',
+    underline: false
+  }
+})
+
+describe('markdown-core spoiler container', () => {
+  it('renders a closed details element with a default title', async () => {
+    const output = await render('::: spoiler\nHidden **content**.\n:::')
+
+    expect(output).toContain('<details class="spoiler"><summary>Spoiler</summary>')
+    expect(output).toContain('<p>Hidden <strong>content</strong>.</p>')
+    expect(output).toContain('</details>')
+  })
+
+  it('supports a custom escaped title', async () => {
+    const output = await render('::: spoiler Reveal <script>alert(1)</script>\nSecret\n:::')
+
+    expect(output).toContain('<summary>Reveal &lt;script&gt;alert(1)&lt;/script&gt;</summary>')
+    expect(output).not.toContain('<summary>Reveal <script>')
+  })
+
+  it('leaves other containers unchanged', async () => {
+    const output = await render('::: note\nVisible\n:::')
+
+    expect(output).toContain('::: note')
+    expect(output).not.toContain('<details')
+  })
+})
diff --git a/yarn.lock b/yarn.lock
index 8414feb3d..7ec62c631 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -13485,6 +13485,11 @@ markdown-it-attrs@3.0.3:
   resolved "https://registry.yarnpkg.com/markdown-it-attrs/-/markdown-it-attrs-3.0.3.tgz#92acdb16fe551cb056c5eb9848413443cafb5231"
   integrity sha512-cLnICU2t61skNCr4Wih/sdza+UbQcqJGZwvqAypnbWA284nzDm+Gpc90iaRk/JjsIy4emag5v3s0rXFhFBWhCA==
 
+markdown-it-container@3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/markdown-it-container/-/markdown-it-container-3.0.0.tgz#1d19b06040a020f9a827577bb7dbf67aa5de9a5b"
+  integrity sha512-y6oKTq4BB9OQuY/KLfk/O3ysFhB3IMYoIWhGJEidXt1NQFocFK2sA2t0NYZAMyMShAGL6x5OPIbrmXPIqaN9rw==
+
 markdown-it-decorate@1.2.2:
   version "1.2.2"
   resolved "https://registry.yarnpkg.com/markdown-it-decorate/-/markdown-it-decorate-1.2.2.tgz#f1e11d11d837ae78906198f8a2c974f0e646acb7"