fix: sanitize shell/subprocess call in CrashLogUtil.kt

tests/test_invariant_CrashLogUtil.kt

@@ -0,0 +1,71 @@
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.io.TempDir
+import org.junit.jupiter.params.ParameterizedTest
+import org.junit.jupiter.params.provider.ValueSource
+import java.io.File
+import eu.kanade.tachiyomi.util.CrashLogUtil
+
+class CrashLogUtilSecurityTest {
+
+    @TempDir
+    lateinit var tempDir: File
+
+    @ParameterizedTest
+    @ValueSource(strings = [
+        "normal_log.txt",
+        "log; rm -rf / #",
+        "log$(whoami).txt",
+        "log`id`.txt",
+        "log.txt; echo injected"
+    ])
+    fun test_logcat_command_injection_prevention(filename: String) {
+        // Property: Shell commands must never include unsanitized user input
+        val testFile = File(tempDir, filename)
+
+        // This test verifies that either:
+        // 1. The command fails safely (exception thrown)
+        // 2. The filename is properly escaped/sanitized
+        // 3. No shell injection occurs
+
+        try {
+            // Call the actual production function
+            CrashLogUtil.dumpLogcatToFile(testFile)
+
+            // If we reach here without exception, verify the file was created
+            // with the exact expected name (not interpreted as shell commands)
+            assert(testFile.exists()) {
+                "File should exist if command executed successfully"
+            }
+
+            // Additional safety check: ensure no unexpected files were created
+            val unexpectedFiles = tempDir.listFiles()?.filter { 
+                it.name != filename && it.name != testFile.name 
+            }
+            assert(unexpectedFiles.isNullOrEmpty()) {
+                "No unexpected files should be created from shell injection: ${unexpectedFiles?.joinToString()}"
+            }
+
+        } catch (e: Exception) {
+            // Acceptable outcome: function throws exception when encountering
+            // problematic characters rather than executing dangerous command
+            assert(e is SecurityException || e is IllegalArgumentException || 
+                   e is IOException || e is RuntimeException) {
+                "Expected safe failure for shell metacharacters, got: ${e.javaClass.simpleName}"
+            }
+        }
+    }
+
+    @Test
+    fun test_valid_input_works() {
+        // Verify normal operation with safe filename
+        val safeFile = File(tempDir, "crash_log.txt")
+
+        // This should work without issues
+        CrashLogUtil.dumpLogcatToFile(safeFile)
+
+        // Verify file was created
+        assert(safeFile.exists()) {
+            "Valid input should create the expected file"
+        }
+    }
+}