diff --git a/src/js/popup.js b/src/js/popup.js
index beb541a..d73cf75 100644
--- a/src/js/popup.js
+++ b/src/js/popup.js
@@ -1092,32 +1092,36 @@ Logic.registerPanel(P_CONTAINER_EDIT, {
     const tabId = currentTab.id;
     const fullURL = this.checkUrl(url);
 
-    // Assign URL to container
-    await Logic.setOrRemoveAssignment(tabId, fullURL, userContextId, false);
+    if (fullURL !== null) { 
+      // Assign URL to container
+      await Logic.setOrRemoveAssignment(tabId, fullURL, userContextId, false);
 
-    // Clear form
-    document.querySelector("#edit-container-panel-site-input").value = "";
+      // Clear form
+      document.querySelector("#edit-container-panel-site-input").value = "";
 
-    // Show new assignments
-    const assignments = await Logic.getAssignmentObjectByContainer(userContextId);
-    this.showAssignedContainers(assignments);
+      // Show new assignments
+      const assignments = await Logic.getAssignmentObjectByContainer(userContextId);
+      this.showAssignedContainers(assignments); 
+    }
   },
 
   checkUrl(url){
     // append "https://" if protocol not found
+    const validUrl = /[\w.-]+(?:\.[\w.-]+)/g;
     const regexWww = /.*www\..*/g;
-    const foundWww = url.match(regexWww);
     const regexhttp = /^http:\/\/.*/g;
     const regexhttps = /^https:\/\/.*/g;
-    const foundhttp = url.match(regexhttp);
-    const foundhttps = url.match(regexhttps);
     let newURL = url;
+    
+    if (!url.match(validUrl)) {
+      return null;
+    }
 
-    if (!foundhttp && !foundhttps) {
+    if (!url.match(regexhttp) && !url.match(regexhttps)) {
       newURL = "https://" + url;
     }
 
-    if (!foundWww) {
+    if (!url.match(regexWww)) {
       if (newURL.match(regexhttp)) {
         newURL = "http://www." + newURL.substring(7);
       } else if (newURL.match(regexhttps)) {
diff --git a/test/issues/1670.test.js b/test/issues/1670.test.js
new file mode 100644
index 0000000..fe8ae84
--- /dev/null
+++ b/test/issues/1670.test.js
@@ -0,0 +1,81 @@
+// const expect = require("chai").expect;
+const {initializeWithTab} = require("../common");
+
+describe("#1670", function () {
+  beforeEach(async function () {
+    this.webExt = await initializeWithTab();
+  });
+
+  afterEach(function () {
+    this.webExt.destroy();
+  });
+
+  describe("creating a new container", function () {
+    beforeEach(async function () {
+      await this.webExt.popup.helper.clickElementById("container-add-link");
+      await this.webExt.popup.helper.clickElementById("edit-container-ok-link");
+    });
+
+    it("should create it in the browser as well", function () {
+      this.webExt.background.browser.contextualIdentities.create.should.have.been.calledOnce;
+    });
+
+    describe("manually assign a valid URL to a container", function () {
+      const exampleUrl = "https://github.com/mozilla/multi-account-containers";
+      beforeEach(async function () {
+        await this.webExt.popup.helper.clickElementById("edit-containers-link");
+        await this.webExt.popup.helper.clickElementByQuerySelectorAll(".edit-container-icon", "last");
+        this.webExt.popup.window.document.getElementById("edit-container-panel-site-input").value = exampleUrl;
+        await this.webExt.popup.helper.clickElementById("edit-container-site-link");
+      });
+
+      it("should assign the URL to a container", function () {
+        this.webExt.background.browser.contextualIdentities.create.should.have.been.calledOnce;
+      });
+    });
+
+    describe("manually assign valid URL without protocol to a container", function () {
+      const exampleUrl = "github.com/mozilla/multi-account-containers";
+      beforeEach(async function () {
+        await this.webExt.popup.helper.clickElementById("edit-containers-link");
+        await this.webExt.popup.helper.clickElementByQuerySelectorAll(".edit-container-icon", "last");
+        this.webExt.popup.window.document.getElementById("edit-container-panel-site-input").value = exampleUrl;
+        await this.webExt.popup.helper.clickElementById("edit-container-site-link");
+      });
+
+      it("should assign the URL without protocol to a container", function () {
+        this.webExt.background.browser.contextualIdentities.create.should.have.been.calledOnce;
+      });
+    });
+
+    describe("manually assign an invalid URL to a container", function () {
+      const exampleUrl = "github";
+      beforeEach(async function () {
+        await this.webExt.popup.helper.clickElementById("edit-containers-link");
+        await this.webExt.popup.helper.clickElementByQuerySelectorAll(".edit-container-icon", "last");
+        this.webExt.popup.window.document.getElementById("edit-container-panel-site-input").value = exampleUrl;
+        await this.webExt.popup.helper.clickElementById("edit-container-site-link");
+      });
+
+      it("should not assign the URL to a container", function () {
+        // console.log(this.webExt.background.browser.contextualIdentities);
+        // expect( console.log.calledOnce ).to.be.true;
+        this.webExt.background.browser.contextualIdentities.update.should.not.have.been.called;
+      });
+    });
+
+    describe("manually assign empty URL to a container", function () {
+      const exampleUrl = "";
+      beforeEach(async function () {
+        await this.webExt.popup.helper.clickElementById("edit-containers-link");
+        await this.webExt.popup.helper.clickElementByQuerySelectorAll(".edit-container-icon", "last");
+        this.webExt.popup.window.document.getElementById("edit-container-panel-site-input").value = exampleUrl;
+        await this.webExt.popup.helper.clickElementById("edit-container-site-link");
+      });
+
+      it("should not assign the URL to a container", function () {
+        this.webExt.background.browser.contextualIdentities.update.should.not.have.been.called;
+      });
+    });
+  });
+});
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