diff --git a/apps/browser/src/autofill/overlay/inline-menu/content/autofill-inline-menu-content.service.spec.ts b/apps/browser/src/autofill/overlay/inline-menu/content/autofill-inline-menu-content.service.spec.ts
index 272bd36d163..174c94f0d47 100644
--- a/apps/browser/src/autofill/overlay/inline-menu/content/autofill-inline-menu-content.service.spec.ts
+++ b/apps/browser/src/autofill/overlay/inline-menu/content/autofill-inline-menu-content.service.spec.ts
@@ -1,6 +1,10 @@
+import { mock } from "jest-mock-extended";
+
 import AutofillInit from "../../../content/autofill-init";
 import { AutofillOverlayElement } from "../../../enums/autofill-overlay.enum";
-import { sendMockExtensionMessage } from "../../../spec/testing-utils";
+import { createMutationRecordMock } from "../../../spec/autofill-mocks";
+import { flushPromises, sendMockExtensionMessage } from "../../../spec/testing-utils";
+import { ElementWithOpId } from "../../../types";
 
 import { AutofillInlineMenuContentService } from "./autofill-inline-menu-content.service";
 
@@ -9,6 +13,7 @@ describe("AutofillInlineMenuContentService", () => {
   let autofillInit: AutofillInit;
   let sendExtensionMessageSpy: jest.SpyInstance;
   let observeBodyMutationsSpy: jest.SpyInstance;
+  const sendResponseSpy = jest.fn();
 
   beforeEach(() => {
     globalThis.document.body.innerHTML = "";
@@ -39,7 +44,7 @@ describe("AutofillInlineMenuContentService", () => {
   });
 
   describe("extension message handlers", () => {
-    describe("closeAutofillInlineMenu", () => {
+    describe("closeAutofillInlineMenu message handler", () => {
       beforeEach(() => {
         observeBodyMutationsSpy.mockImplementation();
       });
@@ -105,7 +110,7 @@ describe("AutofillInlineMenuContentService", () => {
       });
     });
 
-    describe("appendAutofillInlineMenuToDom", () => {
+    describe("appendAutofillInlineMenuToDom message handler", () => {
       beforeEach(() => {
         observeBodyMutationsSpy.mockImplementation();
       });
@@ -137,7 +142,7 @@ describe("AutofillInlineMenuContentService", () => {
       });
     });
 
-    describe("toggleAutofillInlineMenuHidden", () => {
+    describe("toggleAutofillInlineMenuHidden message handler", () => {
       it("sets the inline elements as hidden if the elements do not exist", () => {
         sendMockExtensionMessage({
           command: "toggleAutofillInlineMenuHidden",
@@ -176,5 +181,248 @@ describe("AutofillInlineMenuContentService", () => {
         expect(autofillInlineMenuContentService["isListVisible"]).toBe(false);
       });
     });
+
+    describe("checkIsAutofillInlineMenuButtonVisible message handler", () => {
+      it("returns true if the inline menu button is visible", async () => {
+        autofillInlineMenuContentService["isButtonVisible"] = true;
+
+        sendMockExtensionMessage(
+          { command: "checkIsAutofillInlineMenuButtonVisible" },
+          mock<chrome.runtime.MessageSender>(),
+          sendResponseSpy,
+        );
+        await flushPromises();
+
+        expect(sendResponseSpy).toHaveBeenCalledWith(true);
+      });
+    });
+
+    describe("checkIsAutofillInlineMenuListVisible message handler", () => {
+      it("returns true if the inline menu list is visible", async () => {
+        autofillInlineMenuContentService["isListVisible"] = true;
+
+        sendMockExtensionMessage(
+          { command: "checkIsAutofillInlineMenuListVisible" },
+          mock<chrome.runtime.MessageSender>(),
+          sendResponseSpy,
+        );
+        await flushPromises();
+
+        expect(sendResponseSpy).toHaveBeenCalledWith(true);
+      });
+    });
+  });
+
+  describe("handleInlineMenuElementMutationObserverUpdate", () => {
+    let usernameField: ElementWithOpId<HTMLInputElement>;
+
+    beforeEach(() => {
+      document.body.innerHTML = `
+    <form id="validFormId">
+      <input type="text" id="username-field" placeholder="username" />
+      <input type="password" id="password-field" placeholder="password" />
+    </form>
+    `;
+      usernameField = document.getElementById(
+        "username-field",
+      ) as ElementWithOpId<HTMLInputElement>;
+      usernameField.style.setProperty("display", "block", "important");
+      jest.spyOn(usernameField, "removeAttribute");
+      jest.spyOn(usernameField.style, "setProperty");
+      jest
+        .spyOn(
+          autofillInlineMenuContentService as any,
+          "isTriggeringExcessiveMutationObserverIterations",
+        )
+        .mockReturnValue(false);
+    });
+
+    it("skips handling the mutation if excessive mutation observer events are triggered", () => {
+      jest
+        .spyOn(
+          autofillInlineMenuContentService as any,
+          "isTriggeringExcessiveMutationObserverIterations",
+        )
+        .mockReturnValue(true);
+
+      autofillInlineMenuContentService["handleInlineMenuElementMutationObserverUpdate"]([
+        createMutationRecordMock({ target: usernameField }),
+      ]);
+
+      expect(usernameField.removeAttribute).not.toHaveBeenCalled();
+    });
+
+    it("skips handling the mutation if the record type is not for `attributes`", () => {
+      autofillInlineMenuContentService["handleInlineMenuElementMutationObserverUpdate"]([
+        createMutationRecordMock({ target: usernameField, type: "childList" }),
+      ]);
+
+      expect(usernameField.removeAttribute).not.toHaveBeenCalled();
+    });
+
+    it("removes all element attributes that are not the style attribute", () => {
+      autofillInlineMenuContentService["handleInlineMenuElementMutationObserverUpdate"]([
+        createMutationRecordMock({
+          target: usernameField,
+          type: "attributes",
+          attributeName: "placeholder",
+        }),
+      ]);
+
+      expect(usernameField.removeAttribute).toHaveBeenCalledWith("placeholder");
+    });
+
+    it("removes all attached style attributes and sets the default styles", () => {
+      autofillInlineMenuContentService["handleInlineMenuElementMutationObserverUpdate"]([
+        createMutationRecordMock({
+          target: usernameField,
+          type: "attributes",
+          attributeName: "style",
+        }),
+      ]);
+
+      expect(usernameField.removeAttribute).toHaveBeenCalledWith("style");
+      expect(usernameField.style.setProperty).toHaveBeenCalledWith("all", "initial", "important");
+      expect(usernameField.style.setProperty).toHaveBeenCalledWith(
+        "position",
+        "fixed",
+        "important",
+      );
+      expect(usernameField.style.setProperty).toHaveBeenCalledWith("display", "block", "important");
+    });
+  });
+
+  describe("handleBodyElementMutationObserverUpdate", () => {
+    let buttonElement: HTMLElement;
+    let listElement: HTMLElement;
+
+    beforeEach(() => {
+      document.body.innerHTML = `
+      <div class="overlay-button"></div>
+      <div class="overlay-list"></div>
+      `;
+      buttonElement = document.querySelector(".overlay-button") as HTMLElement;
+      listElement = document.querySelector(".overlay-list") as HTMLElement;
+      autofillInlineMenuContentService["buttonElement"] = buttonElement;
+      autofillInlineMenuContentService["listElement"] = listElement;
+      autofillInlineMenuContentService["isListVisible"] = true;
+      jest.spyOn(globalThis.document.body, "insertBefore");
+      jest
+        .spyOn(
+          autofillInlineMenuContentService as any,
+          "isTriggeringExcessiveMutationObserverIterations",
+        )
+        .mockReturnValue(false);
+    });
+
+    it("skips handling the mutation if the overlay elements are not present in the DOM", () => {
+      autofillInlineMenuContentService["buttonElement"] = undefined;
+      autofillInlineMenuContentService["listElement"] = undefined;
+
+      autofillInlineMenuContentService["handleBodyElementMutationObserverUpdate"]();
+
+      expect(globalThis.document.body.insertBefore).not.toHaveBeenCalled();
+    });
+
+    it("skips handling the mutation if excessive mutations are being triggered", () => {
+      jest
+        .spyOn(
+          autofillInlineMenuContentService as any,
+          "isTriggeringExcessiveMutationObserverIterations",
+        )
+        .mockReturnValue(true);
+
+      autofillInlineMenuContentService["handleBodyElementMutationObserverUpdate"]();
+
+      expect(globalThis.document.body.insertBefore).not.toHaveBeenCalled();
+    });
+
+    it("skips re-arranging the DOM elements if the last child of the body is the overlay list and the second to last child of the body is the overlay button", () => {
+      autofillInlineMenuContentService["handleBodyElementMutationObserverUpdate"]();
+
+      expect(globalThis.document.body.insertBefore).not.toHaveBeenCalled();
+    });
+
+    it("skips re-arranging the DOM elements if the last child is the overlay button and the overlay list is not visible", () => {
+      listElement.remove();
+      autofillInlineMenuContentService["isListVisible"] = false;
+
+      autofillInlineMenuContentService["handleBodyElementMutationObserverUpdate"]();
+
+      expect(globalThis.document.body.insertBefore).not.toHaveBeenCalled();
+    });
+
+    it("positions the overlay button before the overlay list if an element has inserted itself after the button element", () => {
+      const injectedElement = document.createElement("div");
+      document.body.insertBefore(injectedElement, listElement);
+
+      autofillInlineMenuContentService["handleBodyElementMutationObserverUpdate"]();
+
+      expect(globalThis.document.body.insertBefore).toHaveBeenCalledWith(
+        buttonElement,
+        listElement,
+      );
+    });
+
+    it("positions the overlay button before the overlay list if the elements have inserted in incorrect order", () => {
+      document.body.appendChild(buttonElement);
+
+      autofillInlineMenuContentService["handleBodyElementMutationObserverUpdate"]();
+
+      expect(globalThis.document.body.insertBefore).toHaveBeenCalledWith(
+        buttonElement,
+        listElement,
+      );
+    });
+
+    it("positions the last child before the overlay button if it is not the overlay list", () => {
+      const injectedElement = document.createElement("div");
+      document.body.appendChild(injectedElement);
+
+      autofillInlineMenuContentService["handleBodyElementMutationObserverUpdate"]();
+
+      expect(globalThis.document.body.insertBefore).toHaveBeenCalledWith(
+        injectedElement,
+        buttonElement,
+      );
+    });
+  });
+
+  describe("isTriggeringExcessiveMutationObserverIterations", () => {
+    it("clears any existing reset timeout", () => {
+      jest.useFakeTimers();
+      const clearTimeoutSpy = jest.spyOn(globalThis, "clearTimeout");
+      autofillInlineMenuContentService["mutationObserverIterationsResetTimeout"] = setTimeout(
+        jest.fn(),
+        123,
+      );
+
+      autofillInlineMenuContentService["isTriggeringExcessiveMutationObserverIterations"]();
+
+      expect(clearTimeoutSpy).toHaveBeenCalledWith(expect.anything());
+    });
+
+    it("will reset the number of mutationObserverIterations after two seconds", () => {
+      jest.useFakeTimers();
+      autofillInlineMenuContentService["mutationObserverIterations"] = 10;
+
+      autofillInlineMenuContentService["isTriggeringExcessiveMutationObserverIterations"]();
+      jest.advanceTimersByTime(2000);
+
+      expect(autofillInlineMenuContentService["mutationObserverIterations"]).toEqual(0);
+    });
+
+    it("will blur the overlay field and remove the autofill overlay if excessive mutation observer iterations are triggering", async () => {
+      autofillInlineMenuContentService["mutationObserverIterations"] = 101;
+      const closeInlineMenuSpy = jest.spyOn(
+        autofillInlineMenuContentService as any,
+        "closeInlineMenu",
+      );
+
+      autofillInlineMenuContentService["isTriggeringExcessiveMutationObserverIterations"]();
+      await flushPromises();
+
+      expect(closeInlineMenuSpy).toHaveBeenCalled();
+    });
   });
 });