diff --git a/apps/browser/src/autofill/background/abstractions/overlay.background.ts b/apps/browser/src/autofill/background/abstractions/overlay.background.ts
index 58aaa425ac3..3c2b70bb475 100644
--- a/apps/browser/src/autofill/background/abstractions/overlay.background.ts
+++ b/apps/browser/src/autofill/background/abstractions/overlay.background.ts
@@ -96,6 +96,7 @@ type OverlayButtonPortMessageHandlers = {
   [key: string]: CallableFunction;
   overlayButtonClicked: ({ port }: PortConnectionParam) => void;
   closeAutofillOverlay: ({ port }: PortConnectionParam) => void;
+  forceCloseAutofillOverlay: ({ port }: PortConnectionParam) => void;
   overlayPageBlurred: () => void;
   redirectOverlayFocusOut: ({ message, port }: PortOnMessageHandlerParams) => void;
 };
@@ -103,6 +104,7 @@ type OverlayButtonPortMessageHandlers = {
 type OverlayListPortMessageHandlers = {
   [key: string]: CallableFunction;
   checkAutofillOverlayButtonFocused: () => void;
+  forceCloseAutofillOverlay: ({ port }: PortConnectionParam) => void;
   overlayPageBlurred: () => void;
   unlockVault: ({ port }: PortConnectionParam) => void;
   fillSelectedListItem: ({ message, port }: PortOnMessageHandlerParams) => void;
diff --git a/apps/browser/src/autofill/background/overlay.background.spec.ts b/apps/browser/src/autofill/background/overlay.background.spec.ts
index ad6b89cd665..92f0cc1380b 100644
--- a/apps/browser/src/autofill/background/overlay.background.spec.ts
+++ b/apps/browser/src/autofill/background/overlay.background.spec.ts
@@ -1056,13 +1056,29 @@ describe("OverlayBackground", () => {
 
       describe("closeAutofillOverlay", () => {
         it("sends a `closeOverlay` message to the sender tab", () => {
-          jest.spyOn(BrowserApi, "tabSendMessage");
+          jest.spyOn(BrowserApi, "tabSendMessageData");
 
           sendPortMessage(buttonPortSpy, { command: "closeAutofillOverlay" });
 
-          expect(BrowserApi.tabSendMessage).toHaveBeenCalledWith(buttonPortSpy.sender.tab, {
-            command: "closeAutofillOverlay",
-          });
+          expect(BrowserApi.tabSendMessageData).toHaveBeenCalledWith(
+            buttonPortSpy.sender.tab,
+            "closeAutofillOverlay",
+            { forceCloseOverlay: false },
+          );
+        });
+      });
+
+      describe("forceCloseAutofillOverlay", () => {
+        it("sends a `closeOverlay` message to the sender tab with a `forceCloseOverlay` flag of `true` set", () => {
+          jest.spyOn(BrowserApi, "tabSendMessageData");
+
+          sendPortMessage(buttonPortSpy, { command: "forceCloseAutofillOverlay" });
+
+          expect(BrowserApi.tabSendMessageData).toHaveBeenCalledWith(
+            buttonPortSpy.sender.tab,
+            "closeAutofillOverlay",
+            { forceCloseOverlay: true },
+          );
         });
       });
 
@@ -1113,6 +1129,20 @@ describe("OverlayBackground", () => {
         });
       });
 
+      describe("forceCloseAutofillOverlay", () => {
+        it("sends a `closeOverlay` message to the sender tab with a `forceCloseOverlay` flag of `true` set", () => {
+          jest.spyOn(BrowserApi, "tabSendMessageData");
+
+          sendPortMessage(listPortSpy, { command: "forceCloseAutofillOverlay" });
+
+          expect(BrowserApi.tabSendMessageData).toHaveBeenCalledWith(
+            listPortSpy.sender.tab,
+            "closeAutofillOverlay",
+            { forceCloseOverlay: true },
+          );
+        });
+      });
+
       describe("overlayPageBlurred", () => {
         it("checks on the focus state of the overlay button", () => {
           jest.spyOn(overlayBackground as any, "checkOverlayButtonFocused").mockImplementation();
diff --git a/apps/browser/src/autofill/background/overlay.background.ts b/apps/browser/src/autofill/background/overlay.background.ts
index 7d07fb150be..3d6f00ec10f 100644
--- a/apps/browser/src/autofill/background/overlay.background.ts
+++ b/apps/browser/src/autofill/background/overlay.background.ts
@@ -68,11 +68,13 @@ class OverlayBackground implements OverlayBackgroundInterface {
   private readonly overlayButtonPortMessageHandlers: OverlayButtonPortMessageHandlers = {
     overlayButtonClicked: ({ port }) => this.handleOverlayButtonClicked(port),
     closeAutofillOverlay: ({ port }) => this.closeOverlay(port),
+    forceCloseAutofillOverlay: ({ port }) => this.closeOverlay(port, true),
     overlayPageBlurred: () => this.checkOverlayListFocused(),
     redirectOverlayFocusOut: ({ message, port }) => this.redirectOverlayFocusOut(message, port),
   };
   private readonly overlayListPortMessageHandlers: OverlayListPortMessageHandlers = {
     checkAutofillOverlayButtonFocused: () => this.checkOverlayButtonFocused(),
+    forceCloseAutofillOverlay: ({ port }) => this.closeOverlay(port, true),
     overlayPageBlurred: () => this.checkOverlayButtonFocused(),
     unlockVault: ({ port }) => this.unlockVault(port),
     fillSelectedListItem: ({ message, port }) => this.fillSelectedOverlayListItem(message, port),
@@ -268,9 +270,10 @@ class OverlayBackground implements OverlayBackgroundInterface {
    * Sends a message to the sender tab to close the autofill overlay.
    *
    * @param sender - The sender of the port message
+   * @param forceCloseOverlay - Identifies whether the overlay should be force closed
    */
-  private closeOverlay({ sender }: chrome.runtime.Port) {
-    BrowserApi.tabSendMessage(sender.tab, { command: "closeAutofillOverlay" });
+  private closeOverlay({ sender }: chrome.runtime.Port, forceCloseOverlay = false) {
+    BrowserApi.tabSendMessageData(sender.tab, "closeAutofillOverlay", { forceCloseOverlay });
   }
 
   /**
diff --git a/apps/browser/src/autofill/content/abstractions/autofill-init.ts b/apps/browser/src/autofill/content/abstractions/autofill-init.ts
index e15cac15331..139099a4d58 100644
--- a/apps/browser/src/autofill/content/abstractions/autofill-init.ts
+++ b/apps/browser/src/autofill/content/abstractions/autofill-init.ts
@@ -16,6 +16,7 @@ type AutofillExtensionMessage = {
     isOverlayCiphersPopulated?: boolean;
     direction?: "previous" | "next";
     isOpeningFullOverlay?: boolean;
+    forceCloseOverlay?: boolean;
   };
 };
 
@@ -27,7 +28,7 @@ type AutofillExtensionMessageHandlers = {
   collectPageDetailsImmediately: ({ message }: AutofillExtensionMessageParam) => void;
   fillForm: ({ message }: AutofillExtensionMessageParam) => void;
   openAutofillOverlay: ({ message }: AutofillExtensionMessageParam) => void;
-  closeAutofillOverlay: () => void;
+  closeAutofillOverlay: ({ message }: AutofillExtensionMessageParam) => void;
   addNewVaultItemFromOverlay: () => void;
   redirectOverlayFocusOut: ({ message }: AutofillExtensionMessageParam) => void;
   updateIsOverlayCiphersPopulated: ({ message }: AutofillExtensionMessageParam) => void;
diff --git a/apps/browser/src/autofill/content/autofill-init.spec.ts b/apps/browser/src/autofill/content/autofill-init.spec.ts
index 211a6ee03c0..1524fdce100 100644
--- a/apps/browser/src/autofill/content/autofill-init.spec.ts
+++ b/apps/browser/src/autofill/content/autofill-init.spec.ts
@@ -297,6 +297,30 @@ describe("AutofillInit", () => {
           autofillInit["autofillOverlayContentService"].isCurrentlyFilling = false;
         });
 
+        it("skips attempting to remove the overlay if the autofillOverlayContentService is not present", () => {
+          const newAutofillInit = new AutofillInit(undefined);
+          newAutofillInit.init();
+          jest.spyOn(newAutofillInit as any, "removeAutofillOverlay");
+
+          sendExtensionRuntimeMessage({
+            command: "closeAutofillOverlay",
+            data: { forceCloseOverlay: false },
+          });
+
+          expect(newAutofillInit["autofillOverlayContentService"]).toBe(undefined);
+        });
+
+        it("removes the autofill overlay if the message flags a forced closure", () => {
+          sendExtensionRuntimeMessage({
+            command: "closeAutofillOverlay",
+            data: { forceCloseOverlay: true },
+          });
+
+          expect(
+            autofillInit["autofillOverlayContentService"].removeAutofillOverlay,
+          ).toHaveBeenCalled();
+        });
+
         it("ignores the message if a field is currently focused", () => {
           autofillInit["autofillOverlayContentService"].isFieldCurrentlyFocused = true;
 
diff --git a/apps/browser/src/autofill/content/autofill-init.ts b/apps/browser/src/autofill/content/autofill-init.ts
index c2c5a815ef3..9b23305377c 100644
--- a/apps/browser/src/autofill/content/autofill-init.ts
+++ b/apps/browser/src/autofill/content/autofill-init.ts
@@ -20,7 +20,7 @@ class AutofillInit implements AutofillInitInterface {
     collectPageDetailsImmediately: ({ message }) => this.collectPageDetails(message, true),
     fillForm: ({ message }) => this.fillForm(message),
     openAutofillOverlay: ({ message }) => this.openAutofillOverlay(message),
-    closeAutofillOverlay: () => this.removeAutofillOverlay(),
+    closeAutofillOverlay: ({ message }) => this.removeAutofillOverlay(message),
     addNewVaultItemFromOverlay: () => this.addNewVaultItemFromOverlay(),
     redirectOverlayFocusOut: ({ message }) => this.redirectOverlayFocusOut(message),
     updateIsOverlayCiphersPopulated: ({ message }) => this.updateIsOverlayCiphersPopulated(message),
@@ -153,7 +153,12 @@ class AutofillInit implements AutofillInitInterface {
    * If the autofill is currently filling, only the overlay list will be
    * removed.
    */
-  private removeAutofillOverlay() {
+  private removeAutofillOverlay(message?: AutofillExtensionMessage) {
+    if (message?.data?.forceCloseOverlay) {
+      this.autofillOverlayContentService?.removeAutofillOverlay();
+      return;
+    }
+
     if (
       !this.autofillOverlayContentService ||
       this.autofillOverlayContentService.isFieldCurrentlyFocused
diff --git a/apps/browser/src/autofill/overlay/iframe-content/autofill-overlay-iframe.service.spec.ts b/apps/browser/src/autofill/overlay/iframe-content/autofill-overlay-iframe.service.spec.ts
index a9e4ca81cb6..26dc50ecd09 100644
--- a/apps/browser/src/autofill/overlay/iframe-content/autofill-overlay-iframe.service.spec.ts
+++ b/apps/browser/src/autofill/overlay/iframe-content/autofill-overlay-iframe.service.spec.ts
@@ -392,6 +392,23 @@ describe("AutofillOverlayIframeService", () => {
     beforeEach(() => {
       autofillOverlayIframeService.initOverlayIframe({ height: "0px" }, "title", "ariaAlert");
       autofillOverlayIframeService["iframe"].dispatchEvent(new Event(EVENTS.LOAD));
+      portSpy = autofillOverlayIframeService["port"];
+    });
+
+    it("skips handling found mutations if excessive mutations are triggering", async () => {
+      jest.useFakeTimers();
+      jest
+        .spyOn(
+          autofillOverlayIframeService as any,
+          "isTriggeringExcessiveMutationObserverIterations",
+        )
+        .mockReturnValue(true);
+      jest.spyOn(autofillOverlayIframeService as any, "updateElementStyles");
+
+      autofillOverlayIframeService["iframe"].style.visibility = "hidden";
+      await flushPromises();
+
+      expect(autofillOverlayIframeService["updateElementStyles"]).not.toBeCalled();
     });
 
     it("reverts any styles changes made directly to the iframe", async () => {
@@ -402,5 +419,47 @@ describe("AutofillOverlayIframeService", () => {
 
       expect(autofillOverlayIframeService["iframe"].style.visibility).toBe("visible");
     });
+
+    it("force closes the autofill overlay if more than 9 foreign mutations are triggered", async () => {
+      jest.useFakeTimers();
+      autofillOverlayIframeService["foreignMutationsCount"] = 10;
+
+      autofillOverlayIframeService["iframe"].src = "http://malicious-site.com";
+      await flushPromises();
+
+      expect(portSpy.postMessage).toBeCalledWith({ command: "forceCloseAutofillOverlay" });
+    });
+
+    it("force closes the autofill overlay if excessive mutations are being triggered", async () => {
+      jest.useFakeTimers();
+      autofillOverlayIframeService["mutationObserverIterations"] = 20;
+
+      autofillOverlayIframeService["iframe"].src = "http://malicious-site.com";
+      await flushPromises();
+
+      expect(portSpy.postMessage).toBeCalledWith({ command: "forceCloseAutofillOverlay" });
+    });
+
+    it("resets the excessive mutations and foreign mutation counters", async () => {
+      jest.useFakeTimers();
+      autofillOverlayIframeService["foreignMutationsCount"] = 9;
+      autofillOverlayIframeService["mutationObserverIterations"] = 19;
+
+      autofillOverlayIframeService["iframe"].src = "http://malicious-site.com";
+      jest.advanceTimersByTime(2001);
+      await flushPromises();
+
+      expect(autofillOverlayIframeService["foreignMutationsCount"]).toBe(0);
+      expect(autofillOverlayIframeService["mutationObserverIterations"]).toBe(0);
+    });
+
+    it("resets any mutated default attributes for the iframe", async () => {
+      jest.useFakeTimers();
+
+      autofillOverlayIframeService["iframe"].title = "some-other-title";
+      await flushPromises();
+
+      expect(autofillOverlayIframeService["iframe"].title).toBe("title");
+    });
   });
 });
diff --git a/apps/browser/src/autofill/overlay/iframe-content/autofill-overlay-iframe.service.ts b/apps/browser/src/autofill/overlay/iframe-content/autofill-overlay-iframe.service.ts
index dad1e1908e6..20f5aa830fc 100644
--- a/apps/browser/src/autofill/overlay/iframe-content/autofill-overlay-iframe.service.ts
+++ b/apps/browser/src/autofill/overlay/iframe-content/autofill-overlay-iframe.service.ts
@@ -30,6 +30,16 @@ class AutofillOverlayIframeService implements AutofillOverlayIframeServiceInterf
     colorScheme: "normal",
     opacity: "0",
   };
+  private defaultIframeAttributes: Record<string, string> = {
+    src: "",
+    title: "",
+    sandbox: "allow-scripts",
+    allowtransparency: "true",
+    tabIndex: "-1",
+  };
+  private foreignMutationsCount = 0;
+  private mutationObserverIterations = 0;
+  private mutationObserverIterationsResetTimeout: NodeJS.Timeout;
   private readonly windowMessageHandlers: AutofillOverlayIframeWindowMessageHandlers = {
     updateAutofillOverlayListHeight: (message) =>
       this.updateElementStyles(this.iframe, message.styles),
@@ -71,13 +81,14 @@ class AutofillOverlayIframeService implements AutofillOverlayIframeServiceInterf
     iframeTitle: string,
     ariaAlert?: string,
   ) {
+    this.defaultIframeAttributes.src = chrome.runtime.getURL(this.iframePath);
+    this.defaultIframeAttributes.title = iframeTitle;
+
     this.iframe = globalThis.document.createElement("iframe");
-    this.iframe.src = chrome.runtime.getURL(this.iframePath);
     this.updateElementStyles(this.iframe, { ...this.iframeStyles, ...initStyles });
-    this.iframe.tabIndex = -1;
-    this.iframe.setAttribute("title", iframeTitle);
-    this.iframe.setAttribute("sandbox", "allow-scripts");
-    this.iframe.setAttribute("allowtransparency", "true");
+    for (const [attribute, value] of Object.entries(this.defaultIframeAttributes)) {
+      this.iframe.setAttribute(attribute, value);
+    }
     this.iframe.addEventListener(EVENTS.LOAD, this.setupPortMessageListener);
 
     if (ariaAlert) {
@@ -290,9 +301,20 @@ class AutofillOverlayIframeService implements AutofillOverlayIframeServiceInterf
    * @param mutations - The mutations to the iframe element
    */
   private handleMutations = (mutations: MutationRecord[]) => {
+    if (this.isTriggeringExcessiveMutationObserverIterations()) {
+      return;
+    }
+
     for (let index = 0; index < mutations.length; index++) {
       const mutation = mutations[index];
-      if (mutation.type !== "attributes" || mutation.attributeName !== "style") {
+      if (mutation.type !== "attributes") {
+        continue;
+      }
+
+      const element = mutation.target as HTMLElement;
+      if (mutation.attributeName !== "style") {
+        this.handleElementAttributeMutation(element);
+
         continue;
       }
 
@@ -301,6 +323,41 @@ class AutofillOverlayIframeService implements AutofillOverlayIframeServiceInterf
     }
   };
 
+  /**
+   * Handles mutations to the iframe element's attributes. This ensures that
+   * the iframe element's attributes are not modified by a third party source.
+   *
+   * @param element - The element to handle attribute mutations for
+   */
+  private handleElementAttributeMutation(element: HTMLElement) {
+    const attributes = Array.from(element.attributes);
+    for (let attributeIndex = 0; attributeIndex < attributes.length; attributeIndex++) {
+      const attribute = attributes[attributeIndex];
+      if (attribute.name === "style") {
+        continue;
+      }
+
+      if (this.foreignMutationsCount >= 10) {
+        this.port?.postMessage({ command: "forceCloseAutofillOverlay" });
+        break;
+      }
+
+      const defaultIframeAttribute = this.defaultIframeAttributes[attribute.name];
+      if (!defaultIframeAttribute) {
+        this.iframe.removeAttribute(attribute.name);
+        this.foreignMutationsCount++;
+        continue;
+      }
+
+      if (attribute.value === defaultIframeAttribute) {
+        continue;
+      }
+
+      this.iframe.setAttribute(attribute.name, defaultIframeAttribute);
+      this.foreignMutationsCount++;
+    }
+  }
+
   /**
    * Observes the iframe element for mutations to its style attribute.
    */
@@ -314,6 +371,35 @@ class AutofillOverlayIframeService implements AutofillOverlayIframeServiceInterf
   private unobserveIframe() {
     this.iframeMutationObserver.disconnect();
   }
+
+  /**
+   * Identifies if the mutation observer is triggering excessive iterations.
+   * Will remove the autofill overlay if any set mutation observer is
+   * triggering excessive iterations.
+   */
+  private isTriggeringExcessiveMutationObserverIterations() {
+    const resetCounters = () => {
+      this.mutationObserverIterations = 0;
+      this.foreignMutationsCount = 0;
+    };
+
+    if (this.mutationObserverIterationsResetTimeout) {
+      clearTimeout(this.mutationObserverIterationsResetTimeout);
+    }
+
+    this.mutationObserverIterations++;
+    this.mutationObserverIterationsResetTimeout = setTimeout(() => resetCounters(), 2000);
+
+    if (this.mutationObserverIterations > 20) {
+      clearTimeout(this.mutationObserverIterationsResetTimeout);
+      resetCounters();
+      this.port?.postMessage({ command: "forceCloseAutofillOverlay" });
+
+      return true;
+    }
+
+    return false;
+  }
 }
 
 export default AutofillOverlayIframeService;
diff --git a/apps/browser/src/autofill/overlay/pages/list/autofill-overlay-list.ts b/apps/browser/src/autofill/overlay/pages/list/autofill-overlay-list.ts
index b3c20d1edce..053fddb9c13 100644
--- a/apps/browser/src/autofill/overlay/pages/list/autofill-overlay-list.ts
+++ b/apps/browser/src/autofill/overlay/pages/list/autofill-overlay-list.ts
@@ -118,7 +118,9 @@ class AutofillOverlayList extends AutofillOverlayPageElement {
   private updateListItems(ciphers: OverlayCipherData[]) {
     this.ciphers = ciphers;
     this.currentCipherIndex = 0;
-    this.overlayListContainer.innerHTML = "";
+    if (this.overlayListContainer) {
+      this.overlayListContainer.innerHTML = "";
+    }
 
     if (!ciphers?.length) {
       this.buildNoResultsOverlayList();