diff --git a/CHANGES b/CHANGES
index bcad80274be..f666a5b16a9 100644
--- a/CHANGES
+++ b/CHANGES
@@ -17,6 +17,8 @@ Bugs fixed
 ----------
 
 * #8884: html: minified js stemmers not included in the distributed package
+* #8885: html: AttributeError is raised if CSS/JS files are installed via
+  :confval:`html_context`
 * #8880: viewcode: ExtensionError is raised on incremental build after
   unparsable python module found
 
diff --git a/sphinx/builders/html/__init__.py b/sphinx/builders/html/__init__.py
index 6a069c3cad1..c799b017671 100644
--- a/sphinx/builders/html/__init__.py
+++ b/sphinx/builders/html/__init__.py
@@ -1035,8 +1035,20 @@ def hasdoc(name: str) -> bool:
             templatename = newtmpl
 
         # sort JS/CSS before rendering HTML
-        ctx['script_files'].sort(key=lambda js: js.priority)
-        ctx['css_files'].sort(key=lambda css: css.priority)
+        try:
+            # Convert script_files to list to support non-list script_files (refs: #8889)
+            ctx['script_files'] = sorted(list(ctx['script_files']), key=lambda js: js.priority)
+        except AttributeError:
+            # Skip sorting if users modifies script_files directly (maybe via `html_context`).
+            # refs: #8885
+            #
+            # Note: priority sorting feature will not work in this case.
+            pass
+
+        try:
+            ctx['css_files'] = sorted(list(ctx['css_files']), key=lambda css: css.priority)
+        except AttributeError:
+            pass
 
         try:
             output = self.templates.render(templatename, ctx)