diff --git a/web_src/js/features/common-global.js b/web_src/js/features/common-global.js
index c2e011184..0b00eb8e8 100644
--- a/web_src/js/features/common-global.js
+++ b/web_src/js/features/common-global.js
@@ -6,7 +6,7 @@ import {initCompColorPicker} from './comp/ColorPicker.js';
 import {showGlobalErrorMessage} from '../bootstrap.js';
 import {handleGlobalEnterQuickSubmit} from './comp/QuickSubmit.js';
 import {svg} from '../svg.js';
-import {hideElem, showElem, toggleElem} from '../utils/dom.js';
+import {hideElem, showElem, toggleElem, initSubmitEventPolyfill, submitEventSubmitter} from '../utils/dom.js';
 import {htmlEscape} from 'escape-goat';
 import {showTemporaryTooltip} from '../modules/tippy.js';
 import {confirmModal} from './comp/ConfirmModal.js';
@@ -121,7 +121,8 @@ async function formFetchAction(e) {
   const formMethod = formEl.getAttribute('method') || 'get';
   const formActionUrl = formEl.getAttribute('action');
   const formData = new FormData(formEl);
-  const [submitterName, submitterValue] = [e.submitter?.getAttribute('name'), e.submitter?.getAttribute('value')];
+  const formSubmitter = submitEventSubmitter(e);
+  const [submitterName, submitterValue] = [formSubmitter?.getAttribute('name'), formSubmitter?.getAttribute('value')];
   if (submitterName) {
     formData.append(submitterName, submitterValue || '');
   }
@@ -192,6 +193,7 @@ export function initGlobalCommon() {
 
   $('.tabular.menu .item').tab();
 
+  initSubmitEventPolyfill();
   document.addEventListener('submit', formFetchAction);
   document.addEventListener('click', linkAction);
 }
diff --git a/web_src/js/features/common-issue-list.js b/web_src/js/features/common-issue-list.js
index 3a28cf900..317c11219 100644
--- a/web_src/js/features/common-issue-list.js
+++ b/web_src/js/features/common-issue-list.js
@@ -1,5 +1,5 @@
 import $ from 'jquery';
-import {isElemHidden, onInputDebounce, toggleElem} from '../utils/dom.js';
+import {isElemHidden, onInputDebounce, submitEventSubmitter, toggleElem} from '../utils/dom.js';
 import {GET} from '../modules/fetch.js';
 
 const {appSubUrl} = window.config;
@@ -40,7 +40,7 @@ export function initCommonIssueListQuickGoto() {
   $form.on('submit', (e) => {
     // if there is no goto button, or the form is submitted by non-quick-goto elements, submit the form directly
     let doQuickGoto = !isElemHidden($goto);
-    const submitter = e.originalEvent.submitter;
+    const submitter = submitEventSubmitter(e.originalEvent);
     if (submitter !== $form[0] && submitter !== $input[0] && submitter !== $goto[0]) doQuickGoto = false;
     if (!doQuickGoto) return;
 
diff --git a/web_src/js/features/repo-diff.js b/web_src/js/features/repo-diff.js
index e74db04d0..eeb80e91b 100644
--- a/web_src/js/features/repo-diff.js
+++ b/web_src/js/features/repo-diff.js
@@ -7,6 +7,7 @@ import {validateTextareaNonEmpty} from './comp/ComboMarkdownEditor.js';
 import {initViewedCheckboxListenerFor, countAndUpdateViewedFiles, initExpandAndCollapseFilesButton} from './pull-view-file.js';
 import {initImageDiff} from './imagediff.js';
 import {showErrorToast} from '../modules/toast.js';
+import {submitEventSubmitter} from '../utils/dom.js';
 
 const {csrfToken, pageData, i18n} = window.config;
 
@@ -57,7 +58,7 @@ function initRepoDiffConversationForm() {
       const formData = new FormData($form[0]);
 
       // if the form is submitted by a button, append the button's name and value to the form data
-      const submitter = e.originalEvent?.submitter;
+      const submitter = submitEventSubmitter(e.originalEvent);
       const isSubmittedByButton = (submitter?.nodeName === 'BUTTON') || (submitter?.nodeName === 'INPUT' && submitter.type === 'submit');
       if (isSubmittedByButton && submitter.name) {
         formData.append(submitter.name, submitter.value);
diff --git a/web_src/js/modules/tippy.js b/web_src/js/modules/tippy.js
index d27908962..7f8423e31 100644
--- a/web_src/js/modules/tippy.js
+++ b/web_src/js/modules/tippy.js
@@ -106,7 +106,7 @@ function switchTitleToTooltip(target) {
 /**
  * Creating tooltip tippy instance is expensive, so we only create it when the user hovers over the element
  * According to https://www.w3.org/TR/DOM-Level-3-Events/#events-mouseevent-event-order , mouseover event is fired before mouseenter event
- * Some old browsers like Pale Moon doesn't support "mouseenter(capture)"
+ * Some browsers like PaleMoon don't support "addEventListener('mouseenter', capture)"
  * The tippy by default uses "mouseenter" event to show, so we use "mouseover" event to switch to tippy
  * @param e {Event}
  */
diff --git a/web_src/js/utils/dom.js b/web_src/js/utils/dom.js
index 403933883..64a6a5aff 100644
--- a/web_src/js/utils/dom.js
+++ b/web_src/js/utils/dom.js
@@ -194,3 +194,24 @@ export function loadElem(el, src) {
     el.src = src;
   });
 }
+
+// some browsers like PaleMoon don't have "SubmitEvent" support, so polyfill it by a tricky method: use the last clicked button as submitter
+// it can't use other transparent polyfill patches because PaleMoon also doesn't support "addEventListener(capture)"
+const needSubmitEventPolyfill = typeof SubmitEvent === 'undefined';
+
+export function submitEventSubmitter(e) {
+  return needSubmitEventPolyfill ? (e.target._submitter || null) : e.submitter;
+}
+
+function submitEventPolyfillListener(e) {
+  const form = e.target.closest('form');
+  if (!form) return;
+  form._submitter = e.target.closest('button:not([type]), button[type="submit"], input[type="submit"]');
+}
+
+export function initSubmitEventPolyfill() {
+  if (!needSubmitEventPolyfill) return;
+  console.warn(`This browser doesn't have "SubmitEvent" support, use a tricky method to polyfill`);
+  document.body.addEventListener('click', submitEventPolyfillListener);
+  document.body.addEventListener('focus', submitEventPolyfillListener);
+}
diff --git a/web_src/js/webcomponents/webcomponents.js b/web_src/js/webcomponents/webcomponents.js
index b17a4a832..916a588db 100644
--- a/web_src/js/webcomponents/webcomponents.js
+++ b/web_src/js/webcomponents/webcomponents.js
@@ -1,4 +1,4 @@
-import '@webcomponents/custom-elements'; // polyfill for some browsers like Pale Moon
+import '@webcomponents/custom-elements'; // polyfill for some browsers like PaleMoon
 import './polyfill.js';
 
 import '@github/relative-time-element';