diff --git a/.jules/sentinel.md b/.jules/sentinel.md
index a885865d..e42582d6 100644
--- a/.jules/sentinel.md
+++ b/.jules/sentinel.md
@@ -99,3 +99,8 @@
 **Root cause:** The protected implementation added canonical names to the exclusion set but did not compare each observed directory entry through a locale-stable normalized key.
 **Prevention:** Build one `Locale.ROOT` lowercase set from the canonical sensitive names, compare every observed name against it, and add the original spelling to the exclusion set so downstream exact membership remains correct.
 **Evidence:** `testProcessIgnoreFileTreatsSensitiveNamesCaseInsensitively` failed on test-only commit `472b916cd40f70693c4e1eb48956042a25353feb` (CI run `31469596932`) and passed with the source fix at `bb113d858ccfc42ddaecf6729749b238e5ade2d0` (CI run `31469921661`).
+
+## 2026-09-25 - BiDi Text Spoofing 방지
+**Vulnerability:** 파일명에 RTL(Right-to-Left) 오버라이드 등 유니코드 양방향(BiDi) 제어 문자가 포함될 경우 확장자가 위조되는 취약점이 발견되었습니다.
+**Learning:** BiDi 오버라이드는 시각적으로 위험한 파일(예: `.exe`)을 무해한 파일(예: `.txt`)처럼 보이게 만들 수 있습니다. HTML을 렌더링할 때 사용자 통제 영역이 이를 적절히 처리하거나 무효화하지 않으면 XSS 또는 악성 다운로드를 유도할 수 있습니다.
+**Prevention:** HTML 이스케이프 과정에서 유니코드 BiDi 제어 문자(예: `\u202E`)를 이스케이프(예: `\\u202E`)하여 무력화하고, 렌더링된 요소(예: `<title>`, `<a>`의 텍스트)를 `&#x2068;`(FSI) 및 `&#x2069;`(PDI)로 감싸 텍스트 방향성이 문서 내 다른 요소에 영향을 미치지 않도록 격리해야 합니다.
diff --git a/src/main/kotlin/html4tree/main.kt b/src/main/kotlin/html4tree/main.kt
index 0972fa2c..3517b06d 100644
--- a/src/main/kotlin/html4tree/main.kt
+++ b/src/main/kotlin/html4tree/main.kt
@@ -243,6 +243,15 @@ fun String.escapeHtml(): String {
             '"' -> "&quot;"
             '\'' -> "&#x27;"
             '`' -> "&#x60;"
+            '\u202A' -> "\\u202A"
+            '\u202B' -> "\\u202B"
+            '\u202C' -> "\\u202C"
+            '\u202D' -> "\\u202D"
+            '\u202E' -> "\\u202E"
+            '\u2066' -> "\\u2066"
+            '\u2067' -> "\\u2067"
+            '\u2068' -> "\\u2068"
+            '\u2069' -> "\\u2069"
             else -> null
         }
         if (replacement != null) {
@@ -421,12 +430,12 @@ fun process_dir(curr_dir: File, excludeSet: Set<String>? = null, dirFiles: Array
         <!-- 보안 향상: 리퍼러를 통한 디렉토리 경로 노출 방지 -->
         <meta name="referrer" content="no-referrer">
         <meta name="robots" content="noindex, nofollow">
-        <title>${directoryName.escapeHtml()} - 디렉토리 목록</title>
+        <title>&#x2068;${directoryName.escapeHtml()}&#x2069; - 디렉토리 목록</title>
         <style>${CSS_CONTENT}</style>
      </head>
      <body>
        <main>
-         <h1>${directoryName.escapeHtml()}</h1>
+         <h1>&#x2068;${directoryName.escapeHtml()}&#x2069;</h1>
          <nav aria-label="디렉토리 목록">
          <ul role="list">
             <li><a class="dir-link" href="./.." title="상위 디렉토리로 이동"><span class="icon" aria-hidden="true">&#x21B0;</span> <span aria-hidden="true">..</span> <span class="visually-hidden">상위 디렉토리로 이동</span></a></li>
@@ -457,10 +466,10 @@ fun process_dir(curr_dir: File, excludeSet: Set<String>? = null, dirFiles: Array
                }
                if (!isSymbolicLink) {
                   val encodedHref = if (isLinkedDirectory) { "./${fileName.urlEncodePath()}/" } else { "./${fileName.urlEncodePath()}" }
-                  val ariaLabel = "${fileName} ${if (isLinkedDirectory) { "디렉토리" } else { "파일" }}".escapeHtml()
+                  val ariaLabel = "&#x2068;${fileName.escapeHtml()}&#x2069; ${if (isLinkedDirectory) { "디렉토리" } else { "파일" }}"
                   val typeLabel = if (isLinkedDirectory) { "디렉토리" } else { "파일" }
                   val icon = if (isLinkedDirectory) { "&#128193;" } else { "&#128196;" }
-                  l.append("""          <li><a class="dir-link" href="${encodedHref}" title="${ariaLabel}"><span class="icon" aria-hidden="true">${icon}</span> <span>${fileName.escapeHtml()}</span> <span class="visually-hidden">${typeLabel}</span></a></li>""")
+                  l.append("""          <li><a class="dir-link" href="${encodedHref}" aria-label="${ariaLabel}" title="${ariaLabel}"><span class="icon" aria-hidden="true">${icon}</span> <span>&#x2068;${fileName.escapeHtml()}&#x2069;</span> <span class="visually-hidden">${typeLabel}</span></a></li>""")
                   l.append('\n')
                }
            }
diff --git a/src/test/kotlin/html4tree/GeneratedIndexReadabilityTest.kt b/src/test/kotlin/html4tree/GeneratedIndexReadabilityTest.kt
index 5897ce6d..209189cd 100644
--- a/src/test/kotlin/html4tree/GeneratedIndexReadabilityTest.kt
+++ b/src/test/kotlin/html4tree/GeneratedIndexReadabilityTest.kt
@@ -45,9 +45,9 @@ class GeneratedIndexReadabilityTest {
 
         val generatedHtml = generatedHtml()
         val parentIndex = generatedHtml.indexOf("<span aria-hidden=\"true\">..</span>")
-        val firstIndex = generatedHtml.indexOf("alpha.txt")
-        val middleIndex = generatedHtml.indexOf("middle.txt")
-        val lastIndex = generatedHtml.indexOf("zulu.txt")
+        val firstIndex = generatedHtml.indexOf("&#x2068;alpha.txt&#x2069;")
+        val middleIndex = generatedHtml.indexOf("&#x2068;middle.txt&#x2069;")
+        val lastIndex = generatedHtml.indexOf("&#x2068;zulu.txt&#x2069;")
 
         assertTrue(parentIndex >= 0)
         assertTrue(parentIndex < firstIndex)
diff --git a/src/test/kotlin/html4tree/MainTest.kt b/src/test/kotlin/html4tree/MainTest.kt
index 5b76cc5d..a17377ef 100644
--- a/src/test/kotlin/html4tree/MainTest.kt
+++ b/src/test/kotlin/html4tree/MainTest.kt
@@ -60,6 +60,7 @@ class MainTest {
         assertEquals("&amp;&lt;&gt;&quot;&#x27;&#x60;", "&<>\"'`".escapeHtml())
         assertEquals("normal text", "normal text".escapeHtml())
         assertEquals("mix text &amp; and &lt;tag&gt;", "mix text & and <tag>".escapeHtml())
+        assertEquals("bidi\\u202A\\u202B\\u202C\\u202D\\u202E\\u2066\\u2067\\u2068\\u2069chars", "bidi\u202A\u202B\u202C\u202D\u202E\u2066\u2067\u2068\u2069chars".escapeHtml())
     }
 
     @Test
@@ -339,10 +340,12 @@ class MainTest {
         assertTrue(htmlContent.contains("title=\"상위 디렉토리로 이동\""))
         assertTrue(htmlContent.contains("aria-hidden=\"true\""))
         assertTrue(htmlContent.contains("<span class=\"visually-hidden\">파일</span>"))
-        assertTrue(htmlContent.contains("title=\"file1.txt 파일\""))
+        assertTrue(htmlContent.contains("title=\"&#x2068;file1.txt&#x2069; 파일\""))
+        assertTrue(htmlContent.contains("aria-label=\"&#x2068;file1.txt&#x2069; 파일\""))
         assertTrue(htmlContent.contains("<span class=\"visually-hidden\">디렉토리</span>"))
-        assertTrue(htmlContent.contains("title=\"subdir 디렉토리\""))
-        assertTrue(htmlContent.contains("file1.txt"))
+        assertTrue(htmlContent.contains("title=\"&#x2068;subdir&#x2069; 디렉토리\""))
+        assertTrue(htmlContent.contains("aria-label=\"&#x2068;subdir&#x2069; 디렉토리\""))
+        assertTrue(htmlContent.contains("&#x2068;file1.txt&#x2069;"))
         assertTrue(htmlContent.contains("subdir/"))
         assertTrue(htmlContent.contains("&#128193;"))
         assertFalse(htmlContent.contains("test.ignore"))
@@ -942,8 +945,8 @@ class MainTest {
         val indexHtml = File(fakeRoot, "index.html")
         assertTrue(indexHtml.exists())
         val content = indexHtml.readText()
-        assertTrue(content.contains("<title>Root - 디렉토리 목록</title>"))
-        assertTrue(content.contains("<h1>Root</h1>"))
+        assertTrue(content.contains("<title>&#x2068;Root&#x2069; - 디렉토리 목록</title>"))
+        assertTrue(content.contains("<h1>&#x2068;Root&#x2069;</h1>"))
     }
 
 }
