--- a/devtools/client/webconsole/test/browser/browser_webconsole_warning_group_cookies.js
+++ b/devtools/client/webconsole/test/browser/browser_webconsole_warning_group_cookies.js
@@ -99,8 +99,52 @@ add_task(async function testSameSiteCook
       `| ${test.message2}`,
     ]);
 
     await win.close();
   }
 });
 
 add_task(cleanUp);
+
+add_task(async function testInvalidSameSiteMessage() {
+  await pushPref("network.cookie.sameSite.laxByDefault", true);
+
+  const groupLabel =
+    "Some cookies are misusing the “sameSite“ attribute, so it won’t work as expected";
+  const message1 =
+    "Invalid “sameSite“ value for cookie “a”. The supported values are: “lax“, “strict“, “none“.";
+  const message2 =
+    "Cookie “a” has “sameSite” policy set to “lax” because it is missing a “sameSite” attribute, and “sameSite=lax” is the default value for this attribute.";
+
+  const { hud, tab, win } = await openNewWindowAndConsole(
+    "http://example.org/" + TEST_FILE
+  );
+
+  info("Test cookie messages");
+
+  SpecialPowers.spawn(tab.linkedBrowser, [], () => {
+    content.wrappedJSObject.createCookie("a=1; sameSite=batman");
+  });
+
+  const { node } = await waitForMessage(hud, groupLabel, ".warn");
+  is(
+    node.querySelector(".warning-group-badge").textContent,
+    "2",
+    "The badge has the expected text"
+  );
+
+  checkConsoleOutputForWarningGroup(hud, [`▶︎⚠ ${groupLabel} 2`]);
+
+  info("Open the group");
+  node.querySelector(".arrow").click();
+  await waitFor(() => findMessage(hud, "sameSite"));
+
+  checkConsoleOutputForWarningGroup(hud, [
+    `▼︎⚠ ${groupLabel} 2`,
+    `| ${message1}`,
+    `| ${message2}`,
+  ]);
+
+  await win.close();
+});
+
+add_task(cleanUp);

--- a/netwerk/cookie/CookieService.cpp
+++ b/netwerk/cookie/CookieService.cpp
@@ -36,17 +36,18 @@ namespace net {
 /******************************************************************************
  * CookieService impl:
  * useful types & constants
  ******************************************************************************/
 
 static StaticRefPtr<CookieService> gCookieService;
 
 constexpr auto CONSOLE_SAMESITE_CATEGORY = NS_LITERAL_CSTRING("cookieSameSite");
-constexpr auto CONSOLE_GENERIC_CATEGORY = NS_LITERAL_CSTRING("cookies");
+constexpr auto CONSOLE_OVERSIZE_CATEGORY =
+    NS_LITERAL_CSTRING("cookiesOversize");
 
 constexpr auto SAMESITE_MDN_URL = NS_LITERAL_STRING(
     "https://developer.mozilla.org/docs/Web/HTTP/Headers/Set-Cookie/SameSite");
 
 namespace {
 
 // Return false if the cookie should be ignored for the current channel.
 bool ProcessSameSiteCookieForForeignRequest(nsIChannel* aChannel,
@@ -872,17 +873,17 @@ bool CookieService::CanSetCookie(nsIURI*
     AutoTArray<nsString, 2> params = {
         NS_ConvertUTF8toUTF16(aCookieData.name())};
 
     nsString size;
     size.AppendInt(kMaxBytesPerCookie);
     params.AppendElement(size);
 
     LogMessageToConsole(aChannel, aHostURI, nsIScriptError::warningFlag,
-                        CONSOLE_GENERIC_CATEGORY,
+                        CONSOLE_OVERSIZE_CATEGORY,
                         NS_LITERAL_CSTRING("CookieOversize"), params);
     return newCookie;
   }
 
   if (!CookieCommons::CheckName(aCookieData)) {
     COOKIE_LOGFAILURE(SET_COOKIE, aHostURI, savedCookieHeader,
                       "invalid name character");
     return newCookie;
@@ -1277,17 +1278,17 @@ bool CookieService::ParseAttributes(nsIC
         sameSiteSet = true;
       } else if (tokenValue.LowerCaseEqualsLiteral(kSameSiteNone)) {
         aCookieData.sameSite() = nsICookie::SAMESITE_NONE;
         aCookieData.rawSameSite() = nsICookie::SAMESITE_NONE;
         sameSiteSet = true;
       } else {
         LogMessageToConsole(
             aChannel, aHostURI, nsIScriptError::infoFlag,
-            CONSOLE_GENERIC_CATEGORY,
+            CONSOLE_SAMESITE_CATEGORY,
             NS_LITERAL_CSTRING("CookieSameSiteValueInvalid"),
             AutoTArray<nsString, 1>{NS_ConvertUTF8toUTF16(aCookieData.name())});
       }
     }
   }
 
   Telemetry::Accumulate(Telemetry::COOKIE_SAMESITE_SET_VS_UNSET,
                         sameSiteSet ? 1 : 0);
@@ -1648,17 +1649,17 @@ bool CookieService::CheckPath(CookieStru
     AutoTArray<nsString, 2> params = {
         NS_ConvertUTF8toUTF16(aCookieData.name())};
 
     nsString size;
     size.AppendInt(kMaxBytesPerPath);
     params.AppendElement(size);
 
     LogMessageToConsole(aChannel, aHostURI, nsIScriptError::warningFlag,
-                        CONSOLE_GENERIC_CATEGORY,
+                        CONSOLE_OVERSIZE_CATEGORY,
                         NS_LITERAL_CSTRING("CookiePathOversize"), params);
     return false;
   }
 
   if (aCookieData.path().Contains('\t')) {
     return false;
   }