diff --git a/CHANGELOG.md b/CHANGELOG.md
index 76f40bd1d1..bbf142bf7e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,18 @@
 
 All notable changes to this project will be documented in this file.
 
+## [4.3.16] - 2025-12-08
+
+### Security
+
+- Fix inconsistent error handling leaking information on existence of private posts ([GHSA-gwhw-gcjx-72v8](https://github.com/mastodon/mastodon/security/advisories/GHSA-gwhw-gcjx-72v8))
+
+### Fixed
+
+- Fix YouTube embeds by sending referer (#37126 by @ChaosExAnima)
+- Fix YouTube iframe not being able to start at a defined time (#26584 by @BrunoViveiros)
+- Fix known expensive S3 batch delete operation failing because of short timeouts (#37004 by @ClearlyClaire)
+
 ## [4.3.15] - 2025-11-20
 
 ### Fixed
diff --git a/app/controllers/activitypub/likes_controller.rb b/app/controllers/activitypub/likes_controller.rb
index 4aa6a4a771..6de110a272 100644
--- a/app/controllers/activitypub/likes_controller.rb
+++ b/app/controllers/activitypub/likes_controller.rb
@@ -22,7 +22,7 @@ class ActivityPub::LikesController < ActivityPub::BaseController
   def set_status
     @status = @account.statuses.find(params[:status_id])
     authorize @status, :show?
-  rescue Mastodon::NotPermittedError
+  rescue ActiveRecord::RecordNotFound, Mastodon::NotPermittedError
     not_found
   end
 
diff --git a/app/controllers/activitypub/replies_controller.rb b/app/controllers/activitypub/replies_controller.rb
index 0a19275d38..9f4b934d14 100644
--- a/app/controllers/activitypub/replies_controller.rb
+++ b/app/controllers/activitypub/replies_controller.rb
@@ -25,7 +25,7 @@ class ActivityPub::RepliesController < ActivityPub::BaseController
   def set_status
     @status = @account.statuses.find(params[:status_id])
     authorize @status, :show?
-  rescue Mastodon::NotPermittedError
+  rescue ActiveRecord::RecordNotFound, Mastodon::NotPermittedError
     not_found
   end
 
diff --git a/app/controllers/activitypub/shares_controller.rb b/app/controllers/activitypub/shares_controller.rb
index 65b4a5b383..8258278e58 100644
--- a/app/controllers/activitypub/shares_controller.rb
+++ b/app/controllers/activitypub/shares_controller.rb
@@ -22,7 +22,7 @@ class ActivityPub::SharesController < ActivityPub::BaseController
   def set_status
     @status = @account.statuses.find(params[:status_id])
     authorize @status, :show?
-  rescue Mastodon::NotPermittedError
+  rescue ActiveRecord::RecordNotFound, Mastodon::NotPermittedError
     not_found
   end
 
diff --git a/app/controllers/api/v1/polls/votes_controller.rb b/app/controllers/api/v1/polls/votes_controller.rb
index ad1b82cb52..c8cb2d8b0d 100644
--- a/app/controllers/api/v1/polls/votes_controller.rb
+++ b/app/controllers/api/v1/polls/votes_controller.rb
@@ -17,7 +17,7 @@ class Api::V1::Polls::VotesController < Api::BaseController
   def set_poll
     @poll = Poll.attached.find(params[:poll_id])
     authorize @poll.status, :show?
-  rescue Mastodon::NotPermittedError
+  rescue ActiveRecord::RecordNotFound, Mastodon::NotPermittedError
     not_found
   end
 
diff --git a/app/controllers/api/v1/polls_controller.rb b/app/controllers/api/v1/polls_controller.rb
index ffc70a8496..b9d2b2ddd5 100644
--- a/app/controllers/api/v1/polls_controller.rb
+++ b/app/controllers/api/v1/polls_controller.rb
@@ -17,7 +17,7 @@ class Api::V1::PollsController < Api::BaseController
   def set_poll
     @poll = Poll.attached.find(params[:id])
     authorize @poll.status, :show?
-  rescue Mastodon::NotPermittedError
+  rescue ActiveRecord::RecordNotFound, Mastodon::NotPermittedError
     not_found
   end
 
diff --git a/app/controllers/api/v1/statuses/base_controller.rb b/app/controllers/api/v1/statuses/base_controller.rb
index 3f56b68bcf..0c4c49a2c3 100644
--- a/app/controllers/api/v1/statuses/base_controller.rb
+++ b/app/controllers/api/v1/statuses/base_controller.rb
@@ -10,7 +10,7 @@ class Api::V1::Statuses::BaseController < Api::BaseController
   def set_status
     @status = Status.find(params[:status_id])
     authorize @status, :show?
-  rescue Mastodon::NotPermittedError
+  rescue ActiveRecord::RecordNotFound, Mastodon::NotPermittedError
     not_found
   end
 end
diff --git a/app/controllers/api/v1/statuses/bookmarks_controller.rb b/app/controllers/api/v1/statuses/bookmarks_controller.rb
index 109b12f467..b4b976ac3c 100644
--- a/app/controllers/api/v1/statuses/bookmarks_controller.rb
+++ b/app/controllers/api/v1/statuses/bookmarks_controller.rb
@@ -23,7 +23,7 @@ class Api::V1::Statuses::BookmarksController < Api::V1::Statuses::BaseController
     bookmark&.destroy!
 
     render json: @status, serializer: REST::StatusSerializer, relationships: StatusRelationshipsPresenter.new([@status], current_account.id, bookmarks_map: { @status.id => false })
-  rescue Mastodon::NotPermittedError
+  rescue ActiveRecord::RecordNotFound, Mastodon::NotPermittedError
     not_found
   end
 end
diff --git a/app/controllers/api/v1/statuses/favourites_controller.rb b/app/controllers/api/v1/statuses/favourites_controller.rb
index dbc75a0364..17eeccdbe7 100644
--- a/app/controllers/api/v1/statuses/favourites_controller.rb
+++ b/app/controllers/api/v1/statuses/favourites_controller.rb
@@ -25,7 +25,7 @@ class Api::V1::Statuses::FavouritesController < Api::V1::Statuses::BaseControlle
 
     relationships = StatusRelationshipsPresenter.new([@status], current_account.id, favourites_map: { @status.id => false }, attributes_map: { @status.id => { favourites_count: count } })
     render json: @status, serializer: REST::StatusSerializer, relationships: relationships
-  rescue Mastodon::NotPermittedError
+  rescue ActiveRecord::RecordNotFound, Mastodon::NotPermittedError
     not_found
   end
 end
diff --git a/app/controllers/api/v1/statuses/reblogs_controller.rb b/app/controllers/api/v1/statuses/reblogs_controller.rb
index 971b054c54..6a5788fca3 100644
--- a/app/controllers/api/v1/statuses/reblogs_controller.rb
+++ b/app/controllers/api/v1/statuses/reblogs_controller.rb
@@ -36,7 +36,7 @@ class Api::V1::Statuses::ReblogsController < Api::V1::Statuses::BaseController
 
     relationships = StatusRelationshipsPresenter.new([@status], current_account.id, reblogs_map: { @reblog.id => false }, attributes_map: { @reblog.id => { reblogs_count: count } })
     render json: @reblog, serializer: REST::StatusSerializer, relationships: relationships
-  rescue Mastodon::NotPermittedError
+  rescue ActiveRecord::RecordNotFound, Mastodon::NotPermittedError
     not_found
   end
 
@@ -45,7 +45,7 @@ class Api::V1::Statuses::ReblogsController < Api::V1::Statuses::BaseController
   def set_reblog
     @reblog = Status.find(params[:status_id])
     authorize @reblog, :show?
-  rescue Mastodon::NotPermittedError
+  rescue ActiveRecord::RecordNotFound, Mastodon::NotPermittedError
     not_found
   end
 
diff --git a/app/controllers/api/v1/statuses_controller.rb b/app/controllers/api/v1/statuses_controller.rb
index 2593ef7da5..fddd039fe7 100644
--- a/app/controllers/api/v1/statuses_controller.rb
+++ b/app/controllers/api/v1/statuses_controller.rb
@@ -127,7 +127,7 @@ class Api::V1::StatusesController < Api::BaseController
   def set_status
     @status = Status.find(params[:id])
     authorize @status, :show?
-  rescue Mastodon::NotPermittedError
+  rescue ActiveRecord::RecordNotFound, Mastodon::NotPermittedError
     not_found
   end
 
diff --git a/app/controllers/api/web/embeds_controller.rb b/app/controllers/api/web/embeds_controller.rb
index f82c1c50d7..fba56b4058 100644
--- a/app/controllers/api/web/embeds_controller.rb
+++ b/app/controllers/api/web/embeds_controller.rb
@@ -30,7 +30,7 @@ class Api::Web::EmbedsController < Api::Web::BaseController
   def set_status
     @status = Status.find(params[:id])
     authorize @status, :show?
-  rescue Mastodon::NotPermittedError
+  rescue ActiveRecord::RecordNotFound, Mastodon::NotPermittedError
     not_found
   end
 end
diff --git a/app/controllers/authorize_interactions_controller.rb b/app/controllers/authorize_interactions_controller.rb
index 99eed018b0..03cad3e317 100644
--- a/app/controllers/authorize_interactions_controller.rb
+++ b/app/controllers/authorize_interactions_controller.rb
@@ -21,7 +21,7 @@ class AuthorizeInteractionsController < ApplicationController
   def set_resource
     @resource = located_resource
     authorize(@resource, :show?) if @resource.is_a?(Status)
-  rescue Mastodon::NotPermittedError
+  rescue ActiveRecord::RecordNotFound, Mastodon::NotPermittedError
     not_found
   end
 
diff --git a/app/controllers/media_controller.rb b/app/controllers/media_controller.rb
index 9d10468e69..0590ea4027 100644
--- a/app/controllers/media_controller.rb
+++ b/app/controllers/media_controller.rb
@@ -34,7 +34,7 @@ class MediaController < ApplicationController
 
   def verify_permitted_status!
     authorize @media_attachment.status, :show?
-  rescue Mastodon::NotPermittedError
+  rescue ActiveRecord::RecordNotFound, Mastodon::NotPermittedError
     not_found
   end
 
diff --git a/app/controllers/statuses_controller.rb b/app/controllers/statuses_controller.rb
index 341b0e6472..4dcff94bfe 100644
--- a/app/controllers/statuses_controller.rb
+++ b/app/controllers/statuses_controller.rb
@@ -59,7 +59,7 @@ class StatusesController < ApplicationController
   def set_status
     @status = @account.statuses.find(params[:id])
     authorize @status, :show?
-  rescue Mastodon::NotPermittedError
+  rescue ActiveRecord::RecordNotFound, Mastodon::NotPermittedError
     not_found
   end
 
diff --git a/app/javascript/mastodon/features/status/components/card.jsx b/app/javascript/mastodon/features/status/components/card.jsx
index ee1fbe0f8f..161961fdb3 100644
--- a/app/javascript/mastodon/features/status/components/card.jsx
+++ b/app/javascript/mastodon/features/status/components/card.jsx
@@ -37,18 +37,23 @@ const getHostname = url => {
 
 const domParser = new DOMParser();
 
-const addAutoPlay = html => {
+const handleIframeUrl = (html, url, providerName) => {
   const document = domParser.parseFromString(html, 'text/html').documentElement;
   const iframe = document.querySelector('iframe');
+  const startTime = new URL(url).searchParams.get('t');
 
   if (iframe) {
-    if (iframe.src.indexOf('?') !== -1) {
-      iframe.src += '&';
-    } else {
-      iframe.src += '?';
+    const iframeUrl = new URL(iframe.src);
+
+    iframeUrl.searchParams.set('autoplay', 1);
+    iframeUrl.searchParams.set('auto_play', 1);
+
+    if (providerName === 'YouTube') {
+      iframeUrl.searchParams.set('start', startTime || '');
+      iframe.referrerPolicy = 'strict-origin-when-cross-origin';
     }
 
-    iframe.src += 'autoplay=1&auto_play=1';
+    iframe.src = iframeUrl.href;
 
     // DOM parser creates html/body elements around original HTML fragment,
     // so we need to get innerHTML out of the body and not the entire document
@@ -114,7 +119,7 @@ export default class Card extends PureComponent {
 
   renderVideo () {
     const { card } = this.props;
-    const content = { __html: addAutoPlay(card.get('html')) };
+    const content = { __html: handleIframeUrl(card.get('html'), card.get('url'), card.get('provider_name')) };
 
     return (
       <div
diff --git a/app/lib/attachment_batch.rb b/app/lib/attachment_batch.rb
index 374abfac49..1443a1ec60 100644
--- a/app/lib/attachment_batch.rb
+++ b/app/lib/attachment_batch.rb
@@ -112,10 +112,12 @@ class AttachmentBatch
     keys.each_slice(LIMIT) do |keys_slice|
       logger.debug { "Deleting #{keys_slice.size} objects" }
 
-      bucket.delete_objects(delete: {
-        objects: keys_slice.map { |key| { key: key } },
-        quiet: true,
-      })
+      with_overridden_timeout(bucket.client, 120) do
+        bucket.delete_objects(delete: {
+          objects: keys_slice.map { |key| { key: key } },
+          quiet: true,
+        })
+      end
     rescue => e
       retries += 1
 
@@ -134,6 +136,20 @@ class AttachmentBatch
     @bucket ||= records.first.public_send(@attachment_names.first).s3_bucket
   end
 
+  # Currently, the aws-sdk-s3 gem does not offer a way to cleanly override the timeout
+  # per-request. So we change the client's config instead. As this client will likely
+  # be re-used for other jobs, restore its original configuration in an `ensure` block.
+  def with_overridden_timeout(s3_client, longer_read_timeout)
+    original_timeout = s3_client.config.http_read_timeout
+    s3_client.config.http_read_timeout = [original_timeout, longer_read_timeout].max
+
+    begin
+      yield
+    ensure
+      s3_client.config.http_read_timeout = original_timeout
+    end
+  end
+
   def nullified_attributes
     @attachment_names.flat_map { |attachment_name| NULLABLE_ATTRIBUTES.map { |attribute| "#{attachment_name}_#{attribute}" } & klass.column_names }.index_with(nil)
   end
diff --git a/docker-compose.yml b/docker-compose.yml
index c329baf7e7..2a62b23e59 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -27,7 +27,7 @@ services:
 
   # es:
   #   restart: always
-  #   image: docker.elastic.co/elasticsearch/elasticsearch:7.17.4
+  #   image: docker.elastic.co/elasticsearch/elasticsearch:7.17.29
   #   environment:
   #     - "ES_JAVA_OPTS=-Xms512m -Xmx512m -Des.enforce.bootstrap.checks=true"
   #     - "xpack.license.self_generated.type=basic"
@@ -59,7 +59,7 @@ services:
   web:
     # You can uncomment the following line if you want to not use the prebuilt image, for example if you have local code changes
     # build: .
-    image: ghcr.io/glitch-soc/mastodon:v4.3.15
+    image: ghcr.io/glitch-soc/mastodon:v4.3.16
     restart: always
     env_file: .env.production
     command: bundle exec puma -C config/puma.rb
@@ -83,7 +83,7 @@ services:
     # build:
     #   dockerfile: ./streaming/Dockerfile
     #   context: .
-    image: ghcr.io/glitch-soc/mastodon-streaming:v4.3.15
+    image: ghcr.io/glitch-soc/mastodon-streaming:v4.3.16
     restart: always
     env_file: .env.production
     command: node ./streaming/index.js
@@ -102,7 +102,7 @@ services:
   sidekiq:
     # You can uncomment the following line if you want to not use the prebuilt image, for example if you have local code changes
     # build: .
-    image: ghcr.io/glitch-soc/mastodon:v4.3.15
+    image: ghcr.io/glitch-soc/mastodon:v4.3.16
     restart: always
     env_file: .env.production
     command: bundle exec sidekiq
diff --git a/lib/mastodon/version.rb b/lib/mastodon/version.rb
index cdef58d7a9..f5c5223948 100644
--- a/lib/mastodon/version.rb
+++ b/lib/mastodon/version.rb
@@ -13,7 +13,7 @@ module Mastodon
     end
 
     def patch
-      15
+      16
     end
 
     def default_prerelease