diff --git a/.gitignore b/.gitignore
index 649949c..0247737 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,7 @@
 lib
 /runner
 src/plugins.ts
+.claude/
 
 # Created by https://www.toptal.com/developers/gitignore/api/node
 # Edit at https://www.toptal.com/developers/gitignore?templates=node
diff --git a/dist/index.js b/dist/index.js
index 900d796..6308257 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -83059,7 +83059,7 @@ function main() {
             yield (0, plugins_1.registerPlugins)(enablePlugins, tool.version);
         }
         catch (err) {
-            core.setFailed(err.message);
+            core.setFailed(err instanceof Error ? err.message : String(err));
         }
     });
 }
@@ -83090,6 +83090,25 @@ exports.registerPlugins = registerPlugins;
 const shelljs_1 = __importDefault(__nccwpck_require__(1271));
 const semver_1 = __importDefault(__nccwpck_require__(2597));
 const node_fs_1 = __nccwpck_require__(3024);
+/**
+ * Validates enablePlugins input to prevent command injection.
+ * Allows: 'true', 'false', or comma-separated plugin names (alphanumeric, underscore only).
+ */
+function validatePluginInput(input) {
+    // Allow 'true', 'false', or comma-separated identifiers (word characters only)
+    if (!/^(true|false|[\w]+(,[\w]+)*)$/i.test(input)) {
+        throw new Error(`Invalid enable-plugins input: "${input}". Only alphanumeric characters, underscores, and commas are allowed.`);
+    }
+}
+/**
+ * Validates version string to prevent command injection.
+ * Allows: alphanumeric, dots, hyphens (e.g., "0.95.0", "nightly-56ed69a").
+ */
+function validateVersion(version) {
+    if (!/^[\w.-]+$/.test(version)) {
+        throw new Error(`Invalid version format: "${version}". Only alphanumeric characters, dots, and hyphens are allowed.`);
+    }
+}
 const nu = String.raw;
 const pluginRegisterScript = nu `
 #!/usr/bin/env nu
@@ -83159,6 +83178,9 @@ function registerPlugins(enablePlugins, version) {
         if (enablePlugins === '' || enablePlugins === 'false') {
             return;
         }
+        // Validate inputs to prevent command injection
+        validatePluginInput(enablePlugins);
+        validateVersion(version);
         const LEGACY_VERSION = '0.92.3';
         const script = 'register-plugins.nu';
         const isLegacyVersion = !version.includes('nightly') && semver_1.default.lte(version, LEGACY_VERSION);
diff --git a/src/index.ts b/src/index.ts
index a688676..55aa6bd 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -49,7 +49,7 @@ async function main() {
     console.log(`Current directory: ${process.cwd()}`);
     await registerPlugins(enablePlugins, tool.version);
   } catch (err) {
-    core.setFailed(err.message);
+    core.setFailed(err instanceof Error ? err.message : String(err));
   }
 }
 
diff --git a/src/plugins-tpl.ts b/src/plugins-tpl.ts
index fb7b54c..a30abe8 100644
--- a/src/plugins-tpl.ts
+++ b/src/plugins-tpl.ts
@@ -2,6 +2,31 @@ import shell from 'shelljs';
 import semver from 'semver';
 import { promises as fs, constants as fs_constants } from 'node:fs';
 
+/**
+ * Validates enablePlugins input to prevent command injection.
+ * Allows: 'true', 'false', or comma-separated plugin names (alphanumeric, underscore only).
+ */
+function validatePluginInput(input: string): void {
+  // Allow 'true', 'false', or comma-separated identifiers (word characters only)
+  if (!/^(true|false|[\w]+(,[\w]+)*)$/i.test(input)) {
+    throw new Error(
+      `Invalid enable-plugins input: "${input}". Only alphanumeric characters, underscores, and commas are allowed.`
+    );
+  }
+}
+
+/**
+ * Validates version string to prevent command injection.
+ * Allows: alphanumeric, dots, hyphens (e.g., "0.95.0", "nightly-56ed69a").
+ */
+function validateVersion(version: string): void {
+  if (!/^[\w.-]+$/.test(version)) {
+    throw new Error(
+      `Invalid version format: "${version}". Only alphanumeric characters, dots, and hyphens are allowed.`
+    );
+  }
+}
+
 const nu = String.raw;
 
 const pluginRegisterScript = nu`
@@ -12,6 +37,11 @@ export async function registerPlugins(enablePlugins: string, version: string) {
   if (enablePlugins === '' || enablePlugins === 'false') {
     return;
   }
+
+  // Validate inputs to prevent command injection
+  validatePluginInput(enablePlugins);
+  validateVersion(version);
+
   const LEGACY_VERSION = '0.92.3';
   const script = 'register-plugins.nu';
   const isLegacyVersion = !version.includes('nightly') && semver.lte(version, LEGACY_VERSION);
diff --git a/src/plugins.ts b/src/plugins.ts
index 33cc390..1762680 100644
--- a/src/plugins.ts
+++ b/src/plugins.ts
@@ -2,6 +2,31 @@ import shell from 'shelljs';
 import semver from 'semver';
 import { promises as fs, constants as fs_constants } from 'node:fs';
 
+/**
+ * Validates enablePlugins input to prevent command injection.
+ * Allows: 'true', 'false', or comma-separated plugin names (alphanumeric, underscore only).
+ */
+function validatePluginInput(input: string): void {
+  // Allow 'true', 'false', or comma-separated identifiers (word characters only)
+  if (!/^(true|false|[\w]+(,[\w]+)*)$/i.test(input)) {
+    throw new Error(
+      `Invalid enable-plugins input: "${input}". Only alphanumeric characters, underscores, and commas are allowed.`
+    );
+  }
+}
+
+/**
+ * Validates version string to prevent command injection.
+ * Allows: alphanumeric, dots, hyphens (e.g., "0.95.0", "nightly-56ed69a").
+ */
+function validateVersion(version: string): void {
+  if (!/^[\w.-]+$/.test(version)) {
+    throw new Error(
+      `Invalid version format: "${version}". Only alphanumeric characters, dots, and hyphens are allowed.`
+    );
+  }
+}
+
 const nu = String.raw;
 
 const pluginRegisterScript = nu`
@@ -72,6 +97,11 @@ export async function registerPlugins(enablePlugins: string, version: string) {
   if (enablePlugins === '' || enablePlugins === 'false') {
     return;
   }
+
+  // Validate inputs to prevent command injection
+  validatePluginInput(enablePlugins);
+  validateVersion(version);
+
   const LEGACY_VERSION = '0.92.3';
   const script = 'register-plugins.nu';
   const isLegacyVersion = !version.includes('nightly') && semver.lte(version, LEGACY_VERSION);