diff --git a/dist/index.js b/dist/index.js
index 2bfbf1f..242e2f3 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -70472,6 +70472,15 @@ if (require.main === require.cache[eval('__filename')]) {
 const os = __nccwpck_require__(857);
 
 function normalizeVersionName(version) {
+  // The version is interpolated into the release download URL, and the downloaded
+  // archive is extracted and added to PATH. Reject anything that is not a plain tag
+  // name: a value containing "/" or ".." is normalized away by the URL parser and
+  // would point the download at an arbitrary repository, causing the runner to
+  // execute an attacker-supplied binary.
+  if (!/^[A-Za-z0-9][A-Za-z0-9._-]*$/.test(version) || version.includes("..")) {
+    throw new Error(`Invalid version input: '${version}'`);
+  }
+
   const normalized = version.replace(/^nightly-[0-9a-f]{40}$/, "nightly");
   
   // Check if the normalized version is a semver and format it accordingly
diff --git a/src/utils.js b/src/utils.js
index bd9cb9e..0ca185a 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -1,40 +1,49 @@
-const os = require("os");
-
-function normalizeVersionName(version) {
-  const normalized = version.replace(/^nightly-[0-9a-f]{40}$/, "nightly");
-  
-  // Check if the normalized version is a semver and format it accordingly
-  if (/^v?\d+\.\d+\.\d+$/.test(normalized)) {
-    // If it's missing the 'v' prefix, add it
-    const withV = normalized.startsWith("v") ? normalized : `v${normalized}`;
-    // Prepend "foundry-zksync-" to the tag
-    return `foundry-zksync-${withV}`;
-  }
-  return normalized;
-}
-
-function mapArch(arch) {
-  const mappings = {
-    x32: "386",
-    x64: "amd64",
-  };
-
-  return mappings[arch] || arch;
-}
-
-function getDownloadObject(version) {
-  const platform = os.platform();
-  const normalizedVersion = normalizeVersionName(version);
-  const filename = `${normalizedVersion.replaceAll("-", "_")}_${platform}_${mapArch(os.arch())}`;
-  const extension = platform === "win32" ? "zip" : "tar.gz";
-  const url = `https://github.com/matter-labs/foundry-zksync/releases/download/${normalizedVersion}/${filename}.${extension}`;
-
-  return {
-    url,
-    binPath: ".",
-  };
-}
-
-module.exports = {
-  getDownloadObject,
-};
+const os = require("os");
+
+function normalizeVersionName(version) {
+  // The version is interpolated into the release download URL, and the downloaded
+  // archive is extracted and added to PATH. Reject anything that is not a plain tag
+  // name: a value containing "/" or ".." is normalized away by the URL parser and
+  // would point the download at an arbitrary repository, causing the runner to
+  // execute an attacker-supplied binary.
+  if (!/^[A-Za-z0-9][A-Za-z0-9._-]*$/.test(version) || version.includes("..")) {
+    throw new Error(`Invalid version input: '${version}'`);
+  }
+
+  const normalized = version.replace(/^nightly-[0-9a-f]{40}$/, "nightly");
+  
+  // Check if the normalized version is a semver and format it accordingly
+  if (/^v?\d+\.\d+\.\d+$/.test(normalized)) {
+    // If it's missing the 'v' prefix, add it
+    const withV = normalized.startsWith("v") ? normalized : `v${normalized}`;
+    // Prepend "foundry-zksync-" to the tag
+    return `foundry-zksync-${withV}`;
+  }
+  return normalized;
+}
+
+function mapArch(arch) {
+  const mappings = {
+    x32: "386",
+    x64: "amd64",
+  };
+
+  return mappings[arch] || arch;
+}
+
+function getDownloadObject(version) {
+  const platform = os.platform();
+  const normalizedVersion = normalizeVersionName(version);
+  const filename = `${normalizedVersion.replaceAll("-", "_")}_${platform}_${mapArch(os.arch())}`;
+  const extension = platform === "win32" ? "zip" : "tar.gz";
+  const url = `https://github.com/matter-labs/foundry-zksync/releases/download/${normalizedVersion}/${filename}.${extension}`;
+
+  return {
+    url,
+    binPath: ".",
+  };
+}
+
+module.exports = {
+  getDownloadObject,
+};