diff --git a/.jules/sentinel.md b/.jules/sentinel.md
index f900791..aba452c 100644
--- a/.jules/sentinel.md
+++ b/.jules/sentinel.md
@@ -18,10 +18,10 @@
 **Learning:** `File.listFiles()` returns null (not empty) on unreadable directories. Directory crawlers must reject symlink roots, skip symlink children, and avoid enqueueing paths deeper than the configured traversal limit.
 **Prevention:** Use `java.nio.file.Files.isSymbolicLink(file.toPath())` for root and child directory checks, gracefully handle `null` arrays from `listFiles()` and `list()`, and only enqueue child directories when the current level is still below `maxLevel`.
 
-## 2024-06-28 - [html4tree] Static HTML Generation Security
-**Vulnerability:** Defense in Depth (CSP Missing)
-**Learning:** Even when inputs are properly escaped, statically generated HTML that displays file/directory structures should implement a Content Security Policy (CSP) to provide an extra layer of defense against potential XSS bypasses.
-**Prevention:** Include a strict CSP meta tag (e.g., `default-src 'none'; style-src 'unsafe-inline';`) in auto-generated HTML headers when external scripts or resources are not required.
+## 2024-06-28 - [html4tree] 정적 HTML 생성 보안
+**Vulnerability:** 심층 방어 누락 (CSP 누락)
+**Learning:** 입력값이 적절히 이스케이프 되더라도, 파일/디렉토리 구조를 표시하는 정적 생성 HTML은 잠재적인 XSS 우회 공격에 대비하여 추가적인 방어 계층을 제공하는 콘텐츠 보안 정책(CSP)을 반드시 구현해야 합니다.
+**Prevention:** 외부 스크립트나 리소스가 필요하지 않은 경우 자동 생성되는 HTML 헤더에 엄격한 CSP 메타 태그(예: `default-src 'none'; style-src 'nonce-...'; base-uri 'none'; form-action 'none';`)를 포함하고, 스타일 블록에는 일회성 nonce를 부여하십시오.
 
 ## 2024-05-31 - [CRITICAL] 심볼릭 링크 검사 우회 취약점 (canonicalFile)
 **Vulnerability:** `File(path).canonicalFile`를 사용하여 심볼릭 링크 여부를 검사하면, `canonicalFile` 함수 내부에서 심볼릭 링크를 이미 대상(target) 파일의 실제 경로로 해석(resolve)해 버리기 때문에, 이후에 진행되는 `Files.isDirectory(..., LinkOption.NOFOLLOW_LINKS)` 등의 심볼릭 링크 제한 검사가 완전히 무력화되는 취약점이 발견되었습니다.
diff --git a/src/main/kotlin/html4tree/main.kt b/src/main/kotlin/html4tree/main.kt
index f279774..70857a8 100644
--- a/src/main/kotlin/html4tree/main.kt
+++ b/src/main/kotlin/html4tree/main.kt
@@ -1,9 +1,11 @@
 package html4tree
 
 import java.io.File
+import java.security.SecureRandom
 import java.nio.file.Files
 import java.nio.file.LinkOption
 import java.nio.file.StandardCopyOption
+import java.util.Base64
 import com.github.ajalt.clikt.core.CliktCommand
 import com.github.ajalt.clikt.parameters.options.option
 import com.github.ajalt.clikt.parameters.options.default
@@ -21,8 +23,17 @@ class Html4tree : CliktCommand() {
 
 fun main(args: Array<String>)  = Html4tree().main(args)
 
+private val nonceRandom = SecureRandom()
+
+fun generate_csp_nonce(): String {
+    val nonceBytes = ByteArray(16)
+    nonceRandom.nextBytes(nonceBytes)
+    return Base64.getEncoder().encodeToString(nonceBytes)
+}
+
 fun go(topDir: String, maxLevel: Int)  {
     require(topDir.isNotBlank())
+    require(!topDir.contains("..")) { "Path traversal sequences are not allowed." }
     // 보안 수정: symlink 검사를 우회하는 canonicalFile 대신 absoluteFile을 사용
     // canonicalFile은 symlink를 대상 경로로 해석하여 이어지는 NOFOLLOW_LINKS 검사를 무력화합니다.
     val top_dir = File(topDir).absoluteFile.toPath().normalize().toFile()
@@ -44,8 +55,9 @@ fun go(topDir: String, maxLevel: Int)  {
            process_dir(lle.file)
 
         if(maxLevel == -1 || currentLevel < maxLevel) {
+            val exclude = process_ignore_file(lle.file)
             lle.file.listFiles()?.forEach {
-                if(Files.isDirectory(it.toPath(), LinkOption.NOFOLLOW_LINKS)){
+                if(Files.isDirectory(it.toPath(), LinkOption.NOFOLLOW_LINKS) && !Files.isSymbolicLink(it.toPath()) && it.name !in exclude) {
                     ll.push( LinkedListEntry(it, currentLevel+1))
                 }
             }
@@ -176,13 +188,18 @@ fun write_index_file(curr_dir: File, content: String) {
 fun process_dir(curr_dir: File){
     
     val exclude: Set<String> = process_ignore_file(curr_dir)
+    val styleNonce = generate_csp_nonce()
 
     val css = """
-              <style>
+              <style nonce="${styleNonce}">
               ul {
                 list-style-type: none;
                 padding-left: 0;
               }
+              a.dir-link {
+                display: block;
+                width: 100%;
+              }
               a {
                 padding: 0.5rem;
                 text-decoration: none;
@@ -214,6 +231,11 @@ fun process_dir(curr_dir: File){
                   outline-color: #58a6ff;
                 }
               }
+              .empty-dir {
+                padding: 0.5rem;
+                opacity: 0.7;
+                font-style: italic;
+              }
               </style>
               """
 
@@ -223,7 +245,7 @@ fun process_dir(curr_dir: File){
         <meta charset="UTF-8">
         <meta name="viewport" content="width=device-width, initial-scale=1.0">
         <!-- 보안 향상: 인라인 스크립트 실행 방지 -->
-        <meta http-equiv="Content-Security-Policy" content="default-src 'none'; style-src 'unsafe-inline';">
+        <meta http-equiv="Content-Security-Policy" content="default-src 'none'; style-src 'nonce-${styleNonce}'; base-uri 'none'; form-action 'none';">
         <title>${curr_dir.getName().escapeHtml()}</title>
         ${css}
      </head>
@@ -232,7 +254,7 @@ fun process_dir(curr_dir: File){
          <h1>${curr_dir.getName().escapeHtml()}</h1>
          <nav aria-label="디렉토리 목록">
          <ul role="list">
-            <li><a style="display:block; width:100%" href="./.." aria-label="상위 디렉토리로 이동"><span aria-hidden="true">&#x21B0;</span> ..</a></li>
+            <li><a class="dir-link" href="./.." aria-label="상위 디렉토리로 이동"><span aria-hidden="true">&#x21B0;</span> ..</a></li>
 """ 
 
     val index_middle = fun():String{ 
@@ -249,14 +271,14 @@ fun process_dir(curr_dir: File){
                   val encodedHref = if (isLinkedDirectory) { "./${fileName.urlEncodePath()}/" } else { "./${fileName.urlEncodePath()}" }
                   val ariaLabel = "${fileName} ${if (isLinkedDirectory) { "디렉토리" } else { "파일" }}".escapeHtml()
                   val icon = if (isLinkedDirectory) { "&#128193;" } else { "&rtrif;" }
-                  l.append("""          <li><a style="display:block; width:100%" href="${encodedHref}" aria-label="${ariaLabel}"><span aria-hidden="true">${icon}</span> ${fileName.escapeHtml()}</a></li>""")
+                  l.append("""          <li><a class="dir-link" href="${encodedHref}" aria-label="${ariaLabel}"><span aria-hidden="true">${icon}</span> ${fileName.escapeHtml()}</a></li>""")
                   l.append('\n')
                }
            }
         }
 
         if(l.isEmpty()){
-            l.append("""          <li><div style="padding: 0.5rem; opacity: 0.7; font-style: italic;">이 디렉토리는 비어 있습니다.</div></li>""")
+            l.append("""          <li><div class="empty-dir">이 디렉토리는 비어 있습니다.</div></li>""")
             l.append('\n')
         }
 
diff --git a/src/test/kotlin/html4tree/MainTest.kt b/src/test/kotlin/html4tree/MainTest.kt
index e641e85..d3dade6 100644
--- a/src/test/kotlin/html4tree/MainTest.kt
+++ b/src/test/kotlin/html4tree/MainTest.kt
@@ -97,6 +97,13 @@ class MainTest {
         assertTrue(htmlContent.contains("role=\"list\""))
     }
 
+    @Test
+    fun testGoRejectsRelativePathTraversal() {
+        assertFailsWith<IllegalArgumentException> {
+            go("../../../etc/passwd", -1)
+        }
+    }
+
     @Test
     fun testProcessIgnoreFile() {
         val ignoreFile = File(tempDir, ".html4ignore")
@@ -162,7 +169,15 @@ class MainTest {
         assertTrue(htmlContent.contains("&#128193;"))
         assertFalse(htmlContent.contains("test.ignore"))
         assertTrue(htmlContent.contains("Content-Security-Policy"))
-        assertTrue(htmlContent.contains("default-src 'none'; style-src 'unsafe-inline';"))
+        val nonce = Regex("""<style nonce="([A-Za-z0-9+/=]+)">""").find(htmlContent)?.groupValues?.get(1)
+        assertTrue(!nonce.isNullOrBlank(), "style nonce should be rendered")
+        assertTrue(htmlContent.contains("default-src 'none'; style-src 'nonce-${nonce}'"))
+        assertTrue(htmlContent.contains("base-uri 'none'; form-action 'none';"))
+        assertFalse(htmlContent.contains("unsafe-inline"))
+        assertFalse(htmlContent.contains("style=\""))
+        assertTrue(htmlContent.contains("a.dir-link"))
+        assertTrue(htmlContent.contains("class=\"dir-link\""))
+        assertTrue(htmlContent.contains(".empty-dir"))
         assertTrue(htmlContent.contains("prefers-color-scheme: dark"))
     }
 
@@ -249,6 +264,31 @@ class MainTest {
         assertFalse(File(subsubdir, "index.html").exists())
     }
 
+    @Test
+    fun testGoIndexesNormalChildButSkipsSensitiveTraversal() {
+        val subdir = File(tempDir, "subdir")
+        subdir.mkdir()
+        File(tempDir, "plain.txt").writeText("plain")
+        val gitDir = File(tempDir, ".git")
+        gitDir.mkdir()
+
+        go(tempDir.absolutePath, -1)
+
+        assertTrue(File(tempDir, "index.html").exists())
+        assertTrue(File(subdir, "index.html").exists())
+        assertFalse(File(gitDir, "index.html").exists())
+    }
+
+    @Test
+    fun testProcessDirHandlesNonDirectoryWithoutThrowing() {
+        val notADirectory = File(tempDir, "not-a-directory")
+        notADirectory.writeText("content")
+
+        process_dir(notADirectory)
+
+        assertEquals("content", notADirectory.readText())
+    }
+
     @Test
     fun testGoWithUnreadableDir() {
         val unreadableDir = File(tempDir, "unreadable")