diff --git a/packages/backend/src/controller/csrfCheck.ts b/packages/backend/src/controller/csrfCheck.ts
index 5931428..8a6f723 100644
--- a/packages/backend/src/controller/csrfCheck.ts
+++ b/packages/backend/src/controller/csrfCheck.ts
@@ -5,6 +5,15 @@ import { HttpUtils } from "../utils/http";
 const httpUtils = new HttpUtils();
 
 export class CsrfCheck {
+  private nonceParam = [
+    "state",
+    "nonce",
+    "as",
+    "frame_id",
+    "csrf_token",
+    "csrf",
+  ];
+
   private isTargetUri(uri: string): boolean {
     if (
       httpUtils.getQueryParamFromURI(uri, "client_id") !== null &&
@@ -43,105 +52,178 @@ export class CsrfCheck {
     return false;
   }
 
-  private isStateInQuery(request: Request): boolean {
-    const query = request.getQuery();
-    const stateValue =
-      httpUtils.getQueryParam(query || "", "state") ||
-      httpUtils.getQueryParam(query || "", "nonce");
-    if (!stateValue) {
-      return false;
+  private isNonceInQuery(request: Request): boolean {
+    const query = request.getQuery() || "";
+
+    for (const param of this.nonceParam) {
+      if (httpUtils.getQueryParam(query, param) !== null) {
+        return true; // Nonce parameter is present in the query
+      }
     }
-    return true;
+
+    return false; // No nonce parameter found in the query
   }
 
-  private checkStateAtResponseLocationHeader(
+  private getNonceParamName(url: string): string | null {
+    for (const param of this.nonceParam) {
+      if (httpUtils.getQueryParamFromURI(url, param) !== null) {
+        return param; // Return the first matching nonce parameter
+      }
+    }
+
+    return null; // No nonce parameter found
+  }
+
+  private checkNonceAtResponseLocationHeader(
     request: Request,
     response: Response
   ): string[] | 0 {
+    const nonceParamName = this.getNonceParamName(request.getUrl() || "");
+
     if (
-      !(
-        this.isOauthUri(request) &&
-        this.isStateInQuery(request) &&
-        this.isOauthRedirectResponse(response)
-      )
+      !this.isOauthUri(request) ||
+      !this.isNonceInQuery(request) ||
+      !this.isOauthRedirectResponse(response) ||
+      !nonceParamName
     ) {
       return 0; // Not a target, no CSRF risk
     }
 
-    // 요청에서 보낸 state 추출
+    // 요청에서 보낸 Nonce 추출
     const query = request.getQuery() || "";
-    const originalState =
-      httpUtils.getQueryParam(query, "state") ||
-      httpUtils.getQueryParam(query || "", "nonce");
+    const originalNonce = httpUtils.getQueryParam(query, nonceParamName);
 
     // 리다이렉트 URL에서 쿼리 부분만 추출
-    const locationHeader = httpUtils.getHeaderValue(
-      response.getHeaders(),
-      "location"
-    );
-    const responseState =
-      httpUtils.getQueryParamFromURI(locationHeader || "", "state") ||
-      httpUtils.getQueryParamFromURI(locationHeader || "", "nonce");
+    const locationHeader =
+      httpUtils.getHeaderValue(response.getHeaders(), "location") || "";
 
-    // state가 없거나, 요청값과 다르면 CSRF 위험
-    if (!responseState) {
+    const responseNonce = httpUtils.getQueryParamFromURI(
+      locationHeader || "",
+      nonceParamName
+    );
+
+    // Nonce가 없거나, 요청값과 다르면 CSRF 위험
+    if (!responseNonce) {
       // missing state
-      return ["state parameter is missing in the response location header"];
+      return ["Nonce parameter is missing in the response location header"];
     }
-    if (originalState !== responseState) {
+    if (originalNonce !== responseNonce) {
       // mismatch
-      return ["state parameter mismatch between request and response"];
+      return ["Nonce parameter mismatch between request and response"];
     }
 
     return 0; // no CSRF risk detected
   }
 
-  // private async checkStateReuse(
-  //   request: Request,
-  //   originResponse: Response
-  // ): Promise<string[] | 0> {
-  //   // uri에 oauth 관련 파라미터가 없지만, 응답이 oauth 리다이렉트 응답인지 확인
-  //   // 즉, 처음으로 state를 발급한 요청인지 확인
-  //   if (
-  //     !(
-  //       !this.isOauthUri(request) &&
-  //       this.isOauthRedirectResponse(originResponse)
-  //     )
-  //   ) {
-  //     return 0; // Not a target, no CSRF risk
-  //   }
+  private async checkNonceReuse(
+    sdk: SDK<DefineAPI<{}>, {}>,
+    request: Request,
+    originResponse: Response
+  ): Promise<string[] | 0> {
+    // uri에 oauth 관련 파라미터가 없지만, 응답이 oauth 리다이렉트 응답인지 확인
+    // 즉, 처음으로 Nonce를 발급한 요청인지 확인
+    if (
+      this.isOauthUri(request) ||
+      !this.isOauthRedirectResponse(originResponse)
+    ) {
+      return 0; // Not a target, no CSRF risk
+    }
 
-  //   const originResponseLocationHeader = httpUtils.getHeaderValue(
-  //     originResponse.getHeaders(),
-  //     "location"
-  //   );
-  //   const originState = httpUtils.getQueryParamFromURI(
-  //     originResponseLocationHeader || "",
-  //     "state"
-  //   );
+    // 기존 응답의 location 헤더의 url에서 Nonce 파라미터 이름, nonce 파라미터 값, 쿼리 추출
+    const originResponseLocationHeader =
+      httpUtils.getHeaderValue(originResponse.getHeaders(), "location") || "";
+    const nonceParamName =
+      this.getNonceParamName(originResponseLocationHeader || "") || "state";
+    const originLocationQuery =
+      httpUtils.getQueryFromURI(originResponseLocationHeader || "") || "";
+    const originLocationNonce = httpUtils.getQueryParam(
+      originLocationQuery,
+      nonceParamName
+    );
 
-  //   const requestHeaders = request.getHeaders();
-  //   const noCookieHeaders = httpUtils.removeHeaders(requestHeaders, ["cookie"]);
-  //   const newResponse = await httpUtils.resend(request, {
-  //     headers: noCookieHeaders,
-  //   });
-  //   const newLocationHeader = httpUtils.getHeaderValue(
-  //     newResponse.getHeaders(),
-  //     "location"
-  //   );
-  //   const newState = httpUtils.getQueryParamFromURI(
-  //     newLocationHeader || "",
-  //     "state"
-  //   );
+    // 쿠키가 없는 헤더로 새로운 nonce를 발급받기 위해 요청
+    const noCookieHeaders = httpUtils.removeHeaders(request.getHeaders(), [
+      "cookie",
+    ]);
+    const noCookieResponse = await httpUtils.resend(sdk, request, {
+      headers: noCookieHeaders,
+    });
+    if (!noCookieResponse || noCookieResponse?.getCode() >= 400) {
+      return 0;
+    }
 
-  //   if (originState === newState) {
-  //     return [
-  //       "State parameter reused in the response location header, indicating a potential CSRF risk",
-  //     ];
-  //   }
+    // 쿠키가 없는 응답의 location 헤더 추출 및 Nonce 추출
+    const noCookieLocationHeader = httpUtils.getHeaderValue(
+      noCookieResponse?.getHeaders() || {},
+      "location"
+    );
+    const newNonce =
+      httpUtils.getQueryParamFromURI(
+        noCookieLocationHeader || "",
+        nonceParamName
+      ) || "";
 
-  //   return 0; // no CSRF risk detected
-  // }
+    if (originLocationNonce === newNonce) {
+      return [
+        "State parameter reused in the response location header, indicating a potential CSRF risk",
+      ];
+    }
+
+    // 기존 쿠키와 함께 새로운 Nonce로 요청
+    const newQuery = httpUtils.setQueryParam(
+      originLocationQuery,
+      nonceParamName,
+      newNonce
+    );
+
+    // 기존 location 헤더의 uri 요청과 location 헤더에서 nonce값만 새로 발급한 값으로 바꾸어 요청한 결과를 비교
+    const res1 = await httpUtils.customFetch(
+      sdk,
+      originResponseLocationHeader,
+      "GET",
+      originLocationQuery,
+      request.getHeaders()
+    );
+
+    const res2 = await httpUtils.customFetch(
+      sdk,
+      originResponseLocationHeader,
+      "GET",
+      newQuery,
+      request.getHeaders()
+    );
+
+    if (
+      !res1 ||
+      !res2 ||
+      res1.getCode() >= 400 ||
+      res2.getCode() >= 400 ||
+      res1.getCode() !== res2.getCode()
+    ) {
+      return 0;
+    }
+
+    if (
+      res1.getCode() === res2.getCode() &&
+      300 <= res1.getCode() &&
+      res1.getCode() < 400
+    ) {
+      const res1LocationHeader =
+        httpUtils.getHeaderValue(res1.getHeaders(), "location") || "";
+      const res2LocationHeader =
+        httpUtils.getHeaderValue(res2.getHeaders(), "location") || "";
+      const res1ReirectPath = httpUtils.getPathFromURI(res1LocationHeader);
+      const res2ReirectPath = httpUtils.getPathFromURI(res2LocationHeader);
+
+      if (res1ReirectPath === res2ReirectPath) {
+        return [
+          "When nonce parameter reused in the response location header, it might not be verified. Indicating a potential CSRF risk",
+        ];
+      }
+    }
+
+    return 0; // no CSRF risk detected
+  }
 
   async checker(
     sdk: SDK<DefineAPI<{}>, {}>,
@@ -152,7 +234,7 @@ export class CsrfCheck {
 
     // 쿼리에 state 파라미터가 없으면 CSRF 위험
     try {
-      if (this.isOauthUri(request) && !this.isStateInQuery(request)) {
+      if (this.isOauthUri(request) && !this.isNonceInQuery(request)) {
         result += "CSRF risk: missing state parameter"; // CSRF risk: missing state parameter
       }
     } catch (error) {
@@ -162,7 +244,7 @@ export class CsrfCheck {
     // location 헤더에 state 파라미터가 없거나, 요청에서 보낸 state와 다르면 CSRF 위험
     try {
       const stateAtResponseLocationHeaderCheck =
-        this.checkStateAtResponseLocationHeader(request, response);
+        this.checkNonceAtResponseLocationHeader(request, response);
       if (stateAtResponseLocationHeaderCheck !== 0) {
         result += `, ${stateAtResponseLocationHeaderCheck.join(", ")}`;
       }
@@ -172,14 +254,14 @@ export class CsrfCheck {
       );
     }
 
-    // // 처음으로 state를 발급한 요청에서 state 파라미터를 바꿔서 보내기
-    // const reusedStateCheck = await this.checkStateReuse(request, response);
-    // if (reusedStateCheck !== 0) {
-    //   result += `, ${reusedStateCheck.join(", ")}`;
-    // }
+    // 처음으로 state를 발급한 요청에서 state 파라미터를 바꿔서 보내기
+    const reusedStateCheck = await this.checkNonceReuse(sdk, request, response);
+    if (reusedStateCheck !== 0) {
+      result += `, ${reusedStateCheck.join(", ")}`;
+    }
 
-    result.replace(/^\s*,\s*|\s*$/, ""); // Remove leading/trailing commas
     try {
+      result.replace(/^\s*,\s*|\s*$/, ""); // Remove leading/trailing commas
       if (result) {
         await sdk.findings.create({
           title: "csrf vuln",
@@ -187,7 +269,6 @@ export class CsrfCheck {
           request,
           reporter: "csrf reporter",
         });
-        sdk.console.log("qq");
       }
     } catch (error) {
       sdk.console.error(`Error creating finding: ${error}`);
diff --git a/packages/backend/src/utils/http.ts b/packages/backend/src/utils/http.ts
index 9fcd741..01e2cfc 100644
--- a/packages/backend/src/utils/http.ts
+++ b/packages/backend/src/utils/http.ts
@@ -1,3 +1,6 @@
+import type { SDK } from "caido:plugin";
+import { Body, RequestSpec, type Request, type Response } from "caido:utils";
+
 let instance: HttpUtils | null = null;
 export class HttpUtils {
   /**
@@ -11,6 +14,14 @@ export class HttpUtils {
     return instance;
   }
 
+  encodeAndLower(value: string): string {
+    try {
+      return encodeURIComponent(value).toLowerCase();
+    } catch {
+      return value.toLowerCase();
+    }
+  }
+
   /**
    * URI 디코딩 후 소문자로 변환하는 헬퍼 함수
    * @param value - 디코딩하고 소문자로 변환할 문자열
@@ -47,12 +58,35 @@ export class HttpUtils {
     return result;
   }
 
+  getPathFromURI(uri: string): string | null {
+    uri = uri.toLowerCase();
+    try {
+      const urlObj = new URL(uri);
+      const path = urlObj.pathname;
+      return path ? decodeURIComponent(path) : null; // 경로가 없으면 null 반환
+    } catch (e) {
+      return null; // URL 파싱 실패 시 null 반환
+    }
+  }
+
+  getQueryFromURI(uri: string): string | null {
+    uri = uri.toLowerCase();
+    try {
+      const urlObj = new URL(uri);
+      const query = urlObj.search;
+      return query ? decodeURIComponent(query.slice(1)) : null; // 쿼리 문자열에서 ? 제거
+    } catch (e) {
+      return null; // URL 파싱 실패 시 null 반환
+    }
+  }
+
   getQueryParamFromURI(uri: string, key: string): string | null {
-    uri = this.decodeAndLower(uri);
+    uri = uri.toLowerCase();
     key = this.decodeAndLower(key);
     try {
       const urlObj = new URL(uri);
-      return urlObj.searchParams.get(key);
+      const param = urlObj.searchParams.get(key);
+      return param ? decodeURIComponent(param) : null;
     } catch (e) {
       return null;
     }
@@ -66,11 +100,12 @@ export class HttpUtils {
    * @returns      - 해당 파라미터 값, 없으면 null
    */
   getQueryParam(query: string, key: string): string | null {
-    query = this.decodeAndLower(query);
+    query = query.toLowerCase();
     key = this.decodeAndLower(key);
 
     const params = new URLSearchParams(query);
-    return params.get(key);
+    const targetParam = params.get(key);
+    return targetParam ? decodeURIComponent(targetParam) : null;
   }
 
   /**
@@ -82,12 +117,12 @@ export class HttpUtils {
    * @returns      - "a=1&b=2&c=3..." 형태의 새로운 쿼리 문자열
    */
   setQueryParam(query: string, key: string, value: string): string {
-    query = this.decodeAndLower(query);
+    query = query.toLowerCase();
     key = this.decodeAndLower(key);
     value = this.decodeAndLower(value);
 
     const params = new URLSearchParams(query);
-    params.set(key, value);
+    params.set(key, this.encodeAndLower(value));
     return params.toString();
   }
 
@@ -99,7 +134,7 @@ export class HttpUtils {
    * @returns      - 삭제된 상태의 새로운 쿼리 문자열
    */
   removeQueryParam(query: string, key: string): string {
-    query = this.decodeAndLower(query);
+    query = query.toLowerCase();
     key = this.decodeAndLower(key);
 
     const params = new URLSearchParams(query);
@@ -109,6 +144,7 @@ export class HttpUtils {
 
   // Headers
   /**
+   * !! 만약 request.getHeader(`${key}`)을 사용할 수 있다면 이 함수를 사용하지 마세요.
    * 주어진 헤더 맵에서 name에 해당하는 첫 번째 헤더 값을 반환합니다.
    * @param headers     - Response.getHeaders() 가 반환하는 객체
    * @param name        - 꺼내고 싶은 헤더 이름 (예: "location", "Content-Type")
@@ -207,4 +243,89 @@ export class HttpUtils {
     }
     return filtered;
   }
+
+  async resend(
+    sdk: SDK,
+    request: Request,
+    options?: {
+      headers?: Record<string, string | string[]>;
+      body?: Body;
+      method?: string;
+      query?: string;
+    }
+  ): Promise<Response | null> {
+    try {
+      const spec = new RequestSpec(request.getUrl());
+      spec.setMethod(options?.method || request.getMethod() || "GET");
+      if (options?.query) {
+        spec.setQuery(options.query);
+      } else {
+        spec.setQuery(request.getQuery() || "");
+      }
+
+      const originBody = request.getBody();
+      if (options?.body) {
+        spec.setBody(options.body);
+      } else if (originBody) {
+        spec.setBody(originBody);
+      }
+
+      const headers = request.getHeaders();
+      if (options?.headers) {
+        // 기존 헤더에서 options.headers로 덮어쓰기
+        const newHeaders = this.lowerCaseAllHeaders({
+          ...headers,
+          ...options.headers,
+        });
+        for (const [key, value] of Object.entries(newHeaders)) {
+          spec.setHeader(key, Array.isArray(value) ? value.join(", ") : value);
+        }
+      } else {
+        // 기존 헤더 그대로 사용
+        for (const [key, value] of Object.entries(headers)) {
+          spec.setHeader(key, Array.isArray(value) ? value.join(", ") : value);
+        }
+      }
+
+      const result = await sdk.requests.send(spec);
+      return result.response ?? null;
+    } catch (error) {
+      sdk.console.error(
+        `Error resending request to ${request.getUrl()}: ${String(error)}`
+      );
+      return null;
+    }
+  }
+
+  async customFetch(
+    sdk: SDK,
+    url: string,
+    method?: string,
+    query?: string,
+    headers?: Record<string, string | string[]>,
+    body?: Body
+  ): Promise<Response | null> {
+    try {
+      const spec = new RequestSpec(url);
+      spec.setMethod(method || "GET");
+      if (query) {
+        spec.setQuery(query);
+      }
+      if (body) {
+        spec.setBody(body);
+      }
+
+      for (const [key, value] of Object.entries(headers || {})) {
+        spec.setHeader(key, Array.isArray(value) ? value.join(", ") : value);
+      }
+
+      const result = await sdk.requests.send(spec);
+      return result.response ?? null;
+    } catch {
+      sdk.console.error(
+        `Error during custom fetch to ${url}: ${String(error)}`
+      );
+      return null;
+    }
+  }
 }
diff --git a/playground/csrf/index.js b/playground/csrf/index.js
index 5c7a733..01c2bba 100644
--- a/playground/csrf/index.js
+++ b/playground/csrf/index.js
@@ -1,5 +1,6 @@
 // app.js
 const express = require("express");
+const crypto = require("crypto");
 const app = express();
 const port = 8000;
 
@@ -43,8 +44,6 @@ app.get("/authorize/mismatch-state", (req, res) => {
   );
   const code = "authcode-67890";
 
-  console.log(`[VULN] original state from client:`, originalState);
-
   // 클라이언트 state와 다르게 'wrong-state'를 삽입
   const wrongState = "wrong-state";
   const location = `${redirectUri}?code=${code}&state=${wrongState}&client_id=${clientId}`;
@@ -52,6 +51,24 @@ app.get("/authorize/mismatch-state", (req, res) => {
   res.status(302).send(`Redirecting to ${location}`);
 });
 
+/**
+ * 3) 랜덤 state를 생성하여 리다이렉트를 발생시키는 테스트용 엔드포인트
+ *    - /authorize/reuse-state-test 로 접근할 때마다 새로운 16진수 state를 생성
+ *    - 최초 요청에 OAuth 파라미터가 없으므로 isOauthUri(request) == false
+ *    - 응답에 Location 헤더로 '...?state=<랜덤값>' 을 포함
+ *    -> Caido 플러그인의 checkNonceReuse 로직에서 새로운 state가 발급되었는지,
+ *       재사용되었는지를 검증할 수 있음
+ *    - 더하여 callback uri에서 해당 nonce의 유효성을 판단하지 않고 응답 시에 vuln
+ */
+app.get("/authorize/reuse-state-test", (req, res) => {
+  const state = crypto.randomBytes(16).toString("hex");
+
+  // 고정된 콜백 URI로 리다이렉트 (OAuth 파라미터는 여기서만 주입)
+  const location = `http://localhost:${port}/callback?state=${state}&client_id=123`;
+  res.set("Location", location);
+  res.status(302).send(`Redirecting to ${location}`);
+});
+
 app.listen(port, () => {
   console.log(
     `Vulnerable OAuth test server listening at http://localhost:${port}`
@@ -62,4 +79,7 @@ app.listen(port, () => {
   console.log(
     `2) Mismatch-State: http://localhost:${port}/authorize/mismatch-state?client_id=abc&state=xyz&redirect_uri=http://localhost:${port}/callback`
   );
+  console.log(
+    `3) Reuse-State-Test:    http://localhost:${port}/authorize/reuse-state-test`
+  );
 });