diff --git a/src/__tests__/pages/api/services/proxy.test.js b/src/__tests__/pages/api/services/proxy.test.js
index 4d4390697..1bc9a27ed 100644
--- a/src/__tests__/pages/api/services/proxy.test.js
+++ b/src/__tests__/pages/api/services/proxy.test.js
@@ -193,42 +193,61 @@ describe("pages/api/services/proxy", () => {
     widgets.linkwarden.mappings.collections.method = originalMethod;
   });
 
-  it("replaces endpoint segments and rejects unsupported segment keys/values", async () => {
+  it("replaces and encodes endpoint segments", async () => {
     getServiceWidget.mockResolvedValue({ type: "segments" });
     handlerFn.handler.mockImplementation(async (req, res) => res.status(200).json({ endpoint: req.query.endpoint }));
 
-    const res1 = createMockRes();
+    const res = createMockRes();
     await servicesProxy(
       {
         method: "GET",
-        query: { group: "g", service: "s", index: "0", endpoint: "item", segments: JSON.stringify({ id: "123" }) },
+        query: {
+          group: "g",
+          service: "s",
+          index: "0",
+          endpoint: "item",
+          segments: JSON.stringify({ id: "session:123" }),
+        },
       },
-      res1,
+      res,
     );
-    expect(res1.statusCode).toBe(200);
-    expect(res1.body).toEqual({ endpoint: "items/123" });
+    expect(res.statusCode).toBe(200);
+    expect(res.body).toEqual({ endpoint: "items/session%3A123" });
+  });
 
-    const res2 = createMockRes();
-    await servicesProxy(
-      {
-        method: "GET",
-        query: { group: "g", service: "s", index: "0", endpoint: "item", segments: JSON.stringify({ nope: "123" }) },
-      },
-      res2,
-    );
-    expect(res2.statusCode).toBe(403);
-    expect(res2.body).toEqual({ error: "Unsupported segment" });
+  it.each([
+    ["omitted segments", undefined],
+    ["duplicate segment parameters", [JSON.stringify({ id: "123" }), JSON.stringify({ id: "456" })]],
+    ["unsupported keys", JSON.stringify({ nope: "123" })],
+    ["missing keys", JSON.stringify({})],
+    ["extra keys", JSON.stringify({ id: "123", extra: "value" })],
+    ["empty values", JSON.stringify({ id: "" })],
+    ["non-string values", JSON.stringify({ id: 123 })],
+    ["literal traversal", JSON.stringify({ id: "../123" })],
+    ["encoded traversal", JSON.stringify({ id: "%2e%2e%2f123" })],
+    ["double-encoded traversal", JSON.stringify({ id: "%252e%252e%252f123" })],
+    ["encoded slash", JSON.stringify({ id: "session%2f123" })],
+    ["encoded backslash", JSON.stringify({ id: "session%5c123" })],
+    ["malformed encoding", JSON.stringify({ id: "%ZZ" })],
+    ["invalid JSON", "{"],
+    ["arrays", JSON.stringify(["123"])],
+    ["null", "null"],
+  ])("rejects %s in endpoint segments", async (_, segments) => {
+    getServiceWidget.mockResolvedValue({ type: "segments" });
+    handlerFn.handler.mockImplementation(async (req, res) => res.status(200).json({ endpoint: req.query.endpoint }));
 
-    const res3 = createMockRes();
+    const res = createMockRes();
     await servicesProxy(
       {
         method: "GET",
-        query: { group: "g", service: "s", index: "0", endpoint: "item", segments: JSON.stringify({ id: "../123" }) },
+        query: { group: "g", service: "s", index: "0", endpoint: "item", segments },
       },
-      res3,
+      res,
     );
-    expect(res3.statusCode).toBe(403);
-    expect(res3.body).toEqual({ error: "Unsupported segment" });
+
+    expect(res.statusCode).toBe(403);
+    expect(res.body).toEqual({ error: "Unsupported segment" });
+    expect(handlerFn.handler).not.toHaveBeenCalled();
   });
 
   it("adds query params based on mapping params + optionalParams", async () => {
diff --git a/src/pages/api/services/proxy.js b/src/pages/api/services/proxy.js
index b6524972c..8aab61fd7 100644
--- a/src/pages/api/services/proxy.js
+++ b/src/pages/api/services/proxy.js
@@ -7,6 +7,40 @@ import widgets from "widgets/widgets";
 
 const logger = createLogger("servicesProxy");
 
+function getSafeSegments(rawSegments, allowedSegments) {
+  if (typeof rawSegments !== "string" || !Array.isArray(allowedSegments)) return null;
+
+  let segments;
+  try {
+    segments = JSON.parse(rawSegments);
+  } catch {
+    return null;
+  }
+
+  if (!segments || typeof segments !== "object" || Array.isArray(segments)) return null;
+
+  const keys = Object.keys(segments);
+  if (keys.length !== allowedSegments.length || !keys.every((key) => allowedSegments.includes(key))) return null;
+
+  const safeSegments = {};
+  for (const key of allowedSegments) {
+    const value = segments[key];
+    if (
+      typeof value !== "string" ||
+      value.length === 0 ||
+      value.includes("%") ||
+      value.includes("/") ||
+      value.includes("\\") ||
+      value.includes("..")
+    ) {
+      return null;
+    }
+    safeSegments[key] = encodeURIComponent(value);
+  }
+
+  return safeSegments;
+}
+
 export default async function handler(req, res) {
   try {
     const { service, group, index } = req.query;
@@ -55,19 +89,12 @@ export default async function handler(req, res) {
         if (mapping?.body) req.body = mapping?.body;
         req.query.endpoint = endpoint;
 
-        if (req.query.segments) {
-          const segments = JSON.parse(req.query.segments);
-          let validSegments = true;
-          Object.keys(segments).forEach((key) => {
-            if (!mapping.segments.includes(key)) {
-              logger.debug("Unsupported segment: %s", key);
-              validSegments = false;
-            } else if (segments[key].includes("/") || segments[key].includes("\\") || segments[key].includes("..")) {
-              logger.debug("Unsupported segment value: %s", segments[key]);
-              validSegments = false;
-            }
-          });
-          if (!validSegments) return res.status(403).json({ error: "Unsupported segment" });
+        if (mapping.segments || req.query.segments) {
+          const segments = getSafeSegments(req.query.segments, mapping.segments);
+          if (!segments) {
+            logger.debug("Unsupported segments");
+            return res.status(403).json({ error: "Unsupported segment" });
+          }
           req.query.endpoint = formatApiCall(endpoint, segments);
         }