diff --git a/web/e2e-tests/lib/common.ts b/web/e2e-tests/lib/common.ts
index 9c57e27b5c..4cf0dadfec 100644
--- a/web/e2e-tests/lib/common.ts
+++ b/web/e2e-tests/lib/common.ts
@@ -137,7 +137,7 @@ export async function fill_form(
     params: Record<string, boolean | string>,
 ): Promise<void> {
     async function is_dropdown(page: Page, name: string): Promise<boolean> {
-        return (await page.$(`select[name="${name}"]`)) !== null;
+        return (await page.$(`select[name="${CSS.escape(name)}"]`)) !== null;
     }
     for (const name of Object.keys(params)) {
         const name_selector = `${form_selector} [name="${name}"]`;
diff --git a/web/src/compose_banner.ts b/web/src/compose_banner.ts
index 254e9b357f..fa4d1251bf 100644
--- a/web/src/compose_banner.ts
+++ b/web/src/compose_banner.ts
@@ -111,7 +111,12 @@ export function clear_uploads(): void {
 }
 
 export function clear_unmute_topic_notifications(): void {
-    $(`#compose_banners .${CLASSNAMES.unmute_topic_notification.replaceAll(" ", ".")}`).remove();
+    $(
+        `#compose_banners .${CLASSNAMES.unmute_topic_notification
+            .split(" ")
+            .map((classname) => CSS.escape(classname))
+            .join(".")}`,
+    ).remove();
 }
 
 export function clear_all(): void {
diff --git a/web/src/echo.js b/web/src/echo.js
index 52691ff29c..8e4ee6fe97 100644
--- a/web/src/echo.js
+++ b/web/src/echo.js
@@ -465,7 +465,7 @@ function abort_message(message) {
 }
 
 export function display_slow_send_loading_spinner(message) {
-    const $row = $(`div[zid="${message.id}"]`);
+    const $row = $(`div[zid="${CSS.escape(message.id)}"]`);
     if (message.locally_echoed && !message.failed_request) {
         $row.find(".slow-send-spinner").removeClass("hidden");
         // We don't need to do anything special to ensure this gets
diff --git a/web/src/message_lists.js b/web/src/message_lists.js
index bb904ac076..605e297151 100644
--- a/web/src/message_lists.js
+++ b/web/src/message_lists.js
@@ -21,7 +21,7 @@ export function all_rendered_message_lists() {
 }
 
 export function all_current_message_rows() {
-    return $(`#${current.table_name}.message-list .message_row`);
+    return $(`#${CSS.escape(current.table_name)}.message-list .message_row`);
 }
 
 export function update_recipient_bar_background_color() {
diff --git a/web/src/messages_overlay_ui.ts b/web/src/messages_overlay_ui.ts
index a82803c2f9..f5f735948d 100644
--- a/web/src/messages_overlay_ui.ts
+++ b/web/src/messages_overlay_ui.ts
@@ -189,5 +189,5 @@ function scroll_to_element($element: JQuery, context: Context): void {
 }
 
 function get_element_by_id(id: number | string, context: Context): JQuery {
-    return $(`[${context.id_attribute_name}='${id}']`);
+    return $(`[${CSS.escape(context.id_attribute_name)}='${CSS.escape(id.toString())}']`);
 }
diff --git a/web/tests/lib/compose_banner.js b/web/tests/lib/compose_banner.js
index cffd84650c..d3c5bdda64 100644
--- a/web/tests/lib/compose_banner.js
+++ b/web/tests/lib/compose_banner.js
@@ -8,7 +8,12 @@ exports.mock_banners = () => {
     // zjquery doesn't support `remove`, which is used when clearing the compose box.
     // TODO: improve how we test this so that we don't have to mock things like this.
     for (const classname of Object.values(compose_banner.CLASSNAMES)) {
-        $(`#compose_banners .${classname.replaceAll(" ", ".")}`).remove = () => {};
+        $(
+            `#compose_banners .${classname
+                .split(" ")
+                .map((classname) => CSS.escape(classname))
+                .join(".")}`,
+        ).remove = () => {};
     }
     $("#compose_banners .warning").remove = () => {};
     $("#compose_banners .error").remove = () => {};