diff --git a/acquire_bcnum.js b/acquire_bcnum.js
new file mode 100644
index 0000000..ec06154
--- /dev/null
+++ b/acquire_bcnum.js
@@ -0,0 +1,63 @@
+"use strict;"
+async function getAuthToken() {
+    let storageData, dec, tok;
+    storageData = window.sessionStorage.getItem("token");
+    while (!tok) {
+        storageData = window.sessionStorage.getItem("token");
+        dec = JSON.parse(storageData);
+        if (!!dec && Object.keys(dec).includes("accessToken")) {
+            let tokInspect;
+            if (tokInspect && tokInspect.startsWith("eyJ")) {
+                tok = tokInspect;
+            }
+        } else {
+            console.log("No accessToken available. Sleeping...")
+            await new Promise(res => setTimeout(res, 5000));
+        }
+    }
+    return tok;
+}
+function correlationId() {
+    return crypto.randomUUID() + "_" + crypto.randomUUID()
+}
+
+async function getBahncardInfo() {
+    let tok = await getAuthToken();
+    let req = await fetch("https://www.bahn.de/web/api/kundenkonto/bahncard", {
+        headers: [
+            ["Accept", "application/json"], ["authorization", "Bearer " + tok], //["X-Correlation-ID", correlationId()]
+        ]
+    });
+    if (req.ok) {
+        const data = await req.json();
+        console.log(data);
+        const orders = data.bahnCardBestellungen.filter((order) => {
+            return order.bahncardTyp === "BC100" && (Date.parse(order.gueltigAb) < Date.now())
+        });
+        console.log("BahnCard candidates:", orders);
+        if (orders[0] !== undefined) {
+            // Orders are returned in reverse chronological order.
+            // TODO Ask which one if there are multiple.
+            // (Maybe inject a <dialog> element here, those have <input type=radio> and dropdowns.)
+            return orders[0].bcNummer || false;
+        }
+    } else {
+        console.log("Request failed:", req);
+        return false;
+    }
+}
+browser.storage.sync.get("acquireBahncard").then(v => {
+    if (v.acquireBahncard != false) { // may also be undefined, so no identity check here
+        getBahncardInfo().then(v => {
+            if (!!v && v.length == 16) {
+                const saveData = { "bcnum": v, "acquireBahncard": false }
+                console.log("Saving", saveData);
+                browser.storage.sync.set(saveData).then(success => {
+                    if (window !== window.top) {
+                        window.close();
+                    }
+                });
+            }
+        }, f => console.log("Could not acquire BahnCard number.", f))
+    }
+})
\ No newline at end of file
diff --git a/manifest.json b/manifest.json
index 16caa4d..35aec4d 100644
--- a/manifest.json
+++ b/manifest.json
@@ -2,7 +2,7 @@
 	"manifest_version": 2,
 	"name": "BC100 Autofill",
 	"description": "Autofills your BahnCard 100 number and birthday into the passenger rights claim form.",
-	"version": "0.0.3",
+	"version": "0.0.4",
 	"icons": {
 		"64": "icons/icon.png"
 	},
@@ -16,6 +16,16 @@
 			"js": [
 				"content_script.js"
 			]
+		},
+		{
+			"matches": [
+				"https://www.bahn.de/buchung/kundenkonto/bahncard",
+				"https://int.bahn.de/*/buchung/kundenkonto/bahncard",
+				"https://www.bahn.de/buchung/kundenkonto/bahncard?lang=*"
+			],
+			"js": [
+				"acquire_bcnum.js"
+			]
 		}
 	],
 	"permissions": [
diff --git a/options/index.html b/options/index.html
index bcb8e57..0e577b5 100644
--- a/options/index.html
+++ b/options/index.html
@@ -18,6 +18,7 @@
       <span class="sh">The number on the front of your card starting with <span class="ms">7081</span>.</span><br>
       <input name="bcnum" id="bcnum" type="text" pattern="70814[0-9]{11}" required
         title="Your BahnCard number is 16 digits long and starts with 7081." />
+        <button id="bcnum-get-from-profile">Get from profile (experimental)</button>
     </label>
     <label class="item">
       <span class="fh">Your date of birth</span><br>
diff --git a/options/script.js b/options/script.js
index bc7d384..cfe4d2a 100644
--- a/options/script.js
+++ b/options/script.js
@@ -1,3 +1,4 @@
+"use strict;"
 function luhnValidate(cardNumber) {
   cardNumber = String(cardNumber).replace(/[\s]/g, "");
   let odd = false;
@@ -37,7 +38,7 @@ async function saveOptions(ev) {
   clearError();
   ev.preventDefault();
   let bcNum = this.querySelector("#bcnum").value;
-  if (!bcNum.length == 16 || !bcNum.startsWith("70814") || !luhnValidate(bcNum)) {
+  if (bcNum.length !== 16 || !bcNum.startsWith("70814") || !luhnValidate(bcNum)) {
     putError("Your BahnCard number is not valid. Please make sure you haven't made any typos.");
     return;
   }
@@ -75,5 +76,15 @@ async function restoreOptions() {
   document.querySelector("#autocontinue").checked = settings.autocontinue || false;
 }
 
+function startBcnumAcquisition(ev) {
+  browser.storage.sync.set({"acquireBahncard":true}).then(() => {
+    win = window.open("https://www.bahn.de/buchung/kundenkonto/bahncard", "_blank", "popup")
+    if (win instanceof Window){
+      win.postMessage("__WINDOW_OPENED_FOR_BC_ACQUISITION__");
+    }
+  })
+}
+
 document.addEventListener('DOMContentLoaded', restoreOptions);
-document.querySelector("form").addEventListener("submit", saveOptions);
\ No newline at end of file
+document.querySelector("form").addEventListener("submit", saveOptions);
+document.querySelector("#bcnum-get-from-profile").addEventListener("click", startBcnumAcquisition)
\ No newline at end of file