address greptile review feedback (greploop iteration 1)

- storageUtils: fix btoa() crash on non-Latin1 chars by encoding through
  encodeURIComponent before base64
- sanitizeImageSrc: restrict data: URIs to image/* and application/pdf
- useMcpOAuthFlow: restore console.warn on storage failure, document
  localStorage migration fallback removal timeline
- ChatUI: add comment explaining chatHistory persistence origin

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/litellm-dashboard/src/components/playground/chat_ui/ChatUI.tsx

@@ -340,6 +340,10 @@ const ChatUI: React.FC<ChatUIProps> = ({
     proxySettings,
   ]);
 
+  // Note: this debounced chatHistory persistence was part of the original
+  // security-fixes branch (litellm_security_fixes_v1.82.3) and is ported
+  // as-is to keep the cherry-pick faithful. It prevents the synchronous
+  // sessionStorage writes that were flagged by the security scan.
   useEffect(() => {
     if (simplified) return; // Do not persist chat history in simplified (embedded) mode
     const handler = setTimeout(() => {

ui/litellm-dashboard/src/components/playground/chat_ui/ResponsesImageUtils.tsx

@@ -16,12 +16,18 @@ export const sanitizeImageSrc = (url: string | undefined): string => {
     const proto = parsed.protocol;
     if (
       proto === "blob:" ||
-      proto === "data:" ||
       proto === "http:" ||
       proto === "https:"
     ) {
       return parsed.href;
     }
+    // Restrict data: URIs to image and PDF MIME types only
+    if (proto === "data:") {
+      const mime = parsed.pathname.split(";")[0].toLowerCase();
+      if (mime.startsWith("image/") || mime === "application/pdf") {
+        return parsed.href;
+      }
+    }
   } catch {
     // invalid URL — fall through
   }

ui/litellm-dashboard/src/hooks/useMcpOAuthFlow.tsx

@@ -83,13 +83,17 @@ export const useMcpOAuthFlow = ({
   };
 
   const getStorageItem = (key: string): string | null => {
-    // Try obfuscated sessionStorage first, fall back to legacy plain localStorage
+    // Try obfuscated sessionStorage first, fall back to legacy plain localStorage.
+    // The localStorage fallback exists for one-time migration of values written
+    // before the obfuscated-sessionStorage switch. It can be removed once all
+    // active sessions have been refreshed (target: next major release).
     const obfuscated = getObfuscated(key);
     if (obfuscated !== null) return obfuscated;
     if (typeof window === "undefined") return null;
     try {
       return window.localStorage.getItem(key);
     } catch (err) {
+      console.warn(`Failed to read legacy localStorage key "${key}"`, err);
       return null;
     }
   };

ui/litellm-dashboard/src/utils/storageUtils.ts

@@ -10,7 +10,10 @@
 
 export function setObfuscated(key: string, value: string): void {
   try {
-    sessionStorage.setItem(key, btoa(value));
+    // Encode via encodeURIComponent first so non-Latin1 characters
+    // (e.g. Unicode MCP server aliases in OAuth flow-state JSON)
+    // are converted to percent-encoded ASCII before btoa.
+    sessionStorage.setItem(key, btoa(unescape(encodeURIComponent(value))));
   } catch {
     // quota exceeded or SSR — silently drop
   }
@@ -20,7 +23,7 @@ export function getObfuscated(key: string): string | null {
   try {
     const raw = sessionStorage.getItem(key);
     if (raw === null) return null;
-    return atob(raw);
+    return decodeURIComponent(escape(atob(raw)));
   } catch {
     // invalid base64 or SSR — treat as missing
     return null;