Merge commit from fork

* Check scheme in account and post links

* Harden media attachments

* Client-side mitigation

* Client-side mitigation for media attachments

app/lib/activitypub/parser/media_attachment_parser.rb

@@ -15,13 +15,15 @@ class ActivityPub::Parser::MediaAttachmentParser
   end
 
   def remote_url
-    Addressable::URI.parse(@json['url'])&.normalize&.to_s
+    url = Addressable::URI.parse(@json['url'])&.normalize&.to_s
+    url unless unsupported_uri_scheme?(url)
   rescue Addressable::URI::InvalidURIError
     nil
   end
 
   def thumbnail_remote_url
-    Addressable::URI.parse(@json['icon'].is_a?(Hash) ? @json['icon']['url'] : @json['icon'])&.normalize&.to_s
+    url = Addressable::URI.parse(@json['icon'].is_a?(Hash) ? @json['icon']['url'] : @json['icon'])&.normalize&.to_s
+    url unless unsupported_uri_scheme?(url)
   rescue Addressable::URI::InvalidURIError
     nil
   end

app/lib/activitypub/parser/status_parser.rb

@@ -29,7 +29,10 @@ class ActivityPub::Parser::StatusParser
   end
 
   def url
-    url_to_href(@object['url'], 'text/html') if @object['url'].present?
+    return if @object['url'].blank?
+
+    url = url_to_href(@object['url'], 'text/html')
+    url unless unsupported_uri_scheme?(url)
   end
 
   def text

app/lib/activitypub/tag_manager.rb

@@ -4,6 +4,7 @@ require 'singleton'
 
 class ActivityPub::TagManager
   include Singleton
+  include JsonLdHelper
   include RoutingHelper
 
   CONTEXT = 'https://www.w3.org/ns/activitystreams'
@@ -17,7 +18,7 @@ class ActivityPub::TagManager
   end
 
   def url_for(target)
-    return target.url if target.respond_to?(:local?) && !target.local?
+    return unsupported_uri_scheme?(target.url) ? nil : target.url if target.respond_to?(:local?) && !target.local?
 
     return unless target.respond_to?(:object_type)