diff --git a/src/data-sources/data-registration.ts b/src/data-sources/data-registration.ts
index 8573c20..abd722a 100644
--- a/src/data-sources/data-registration.ts
+++ b/src/data-sources/data-registration.ts
@@ -1,4 +1,5 @@
 import { attackDomainSchema, type AttackDomain } from "../schemas/index.js";
+import { fetchAttackVersions } from "./fetch-attack-versions.js";
 
 export type ParsingMode = 'strict' | 'relaxed';
 
@@ -25,59 +26,87 @@ export type DataSourceOptions =
         parsingMode?: ParsingMode;
     };
 
-// DataRegistration class with validation logic
+/**
+ * Represents a data source registration with validation logic.
+ */
 export class DataRegistration {
-    constructor(public options: DataSourceOptions) {
-        // Validate the provided options when an instance is created
+    /**
+     * Creates a new DataRegistration instance.
+     * @param options - The data source options to register.
+     */
+    constructor(public readonly options: DataSourceOptions) {
         this.validateOptions();
     }
 
     /**
      * Validates the data source options to ensure the correct fields are provided for each source type.
-     * Throws an error if validation fails.
+     * @throws An error if validation fails.
      */
-    private validateOptions(): void {
+    private async validateOptions(): Promise<void> {
         const { source, parsingMode } = this.options;
 
-        // Validate parsingMode
+        // Validate parsing mode
         if (parsingMode && !['strict', 'relaxed'].includes(parsingMode)) {
             throw new Error(`Invalid parsingMode: ${parsingMode}. Expected 'strict' or 'relaxed'.`);
         }
 
         switch (source) {
             case 'attack': {
-                const { domain } = this.options as { domain: AttackDomain };
-                if (!domain || !Object.values(attackDomainSchema.enum).includes(domain)) {
-                    throw new Error(
-                        `Invalid domain provided for 'attack' source. Expected one of: ${Object.values(
-                            attackDomainSchema.enum
-                        ).join(', ')}`
-                    );
-                }
+                await this.validateAttackOptions();
                 break;
             }
             case 'file': {
-                const { path } = this.options as { path: string };
-                if (!path) {
-                    throw new Error(
-                        "The 'file' source requires a 'path' field to specify the file location."
-                    );
-                }
+                this.validateFileOptions();
                 break;
             }
             case 'url':
             case 'taxii': {
-                const { url } = this.options as { url: string };
-                if (!url) {
-                    throw new Error(
-                        `The '${source}' source requires a 'url' field to specify the data location.`
-                    );
-                }
-                break;
+                throw new Error(`The ${source} source is not implemented yet.`);
             }
             default: {
                 throw new Error(`Unsupported data source type: ${source}`);
             }
         }
     }
-}
+
+    /**
+     * Validates options specific to the 'attack' source type.
+     * @throws An error if validation fails.
+     */
+    private async validateAttackOptions(): Promise<void> {
+        const { domain, version } = this.options as { domain: AttackDomain; version?: string };
+
+        // Validate domain
+        if (!domain || !Object.values(attackDomainSchema.enum).includes(domain)) {
+            throw new Error(
+                `Invalid domain provided for 'attack' source. Expected one of: ${Object.values(
+                    attackDomainSchema.enum
+                ).join(', ')}`
+            );
+        }
+
+        // Validate version if provided
+        if (version) {
+            const supportedVersions = await fetchAttackVersions();
+            const normalizedVersion = version.replace(/^v/, ''); // Remove leading 'v' if present
+            if (!supportedVersions.includes(normalizedVersion)) {
+                throw new Error(
+                    `Invalid version: ${version}. Supported versions are: ${supportedVersions.join(', ')}`
+                );
+            }
+        }
+    }
+
+    /**
+     * Validates options specific to the 'file' source type.
+     * @throws An error if validation fails.
+     */
+    private validateFileOptions(): void {
+        const { path } = this.options as { path: string };
+        if (!path) {
+            throw new Error(
+                "The 'file' source requires a 'path' field to specify the file location."
+            );
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/data-sources/fetch-attack-versions.ts b/src/data-sources/fetch-attack-versions.ts
new file mode 100644
index 0000000..228494e
--- /dev/null
+++ b/src/data-sources/fetch-attack-versions.ts
@@ -0,0 +1,52 @@
+/**
+ * Represents a GitHub release object.
+ */
+interface GitHubRelease {
+    tag_name: string;
+    name: string;
+    published_at: string;
+}
+
+/**
+ * Normalizes a version string by removing any leading 'v' character.
+ * @param version - The version string to normalize.
+ * @returns The normalized version string.
+ */
+function normalizeVersion(version: string): string {
+    return version.replace(/^v/, '');
+}
+
+/**
+ * Fetches the list of ATT&CK versions from the MITRE ATT&CK STIX data GitHub repository.
+ * @returns A promise that resolves to an array of version strings.
+ * @throws An error if the HTTP request fails.
+ */
+export async function fetchAttackVersions(): Promise<string[]> {
+    const url = 'https://api.github.com/repos/mitre-attack/attack-stix-data/releases';
+
+    // Make a GET request to the GitHub API
+    const response = await fetch(url, {
+        headers: {
+            'Accept': 'application/vnd.github+json',
+            'X-GitHub-Api-Version': '2022-11-28'
+        }
+    });
+
+    if (!response.ok) {
+        throw new Error(`HTTP error! status: ${response.status}`);
+    }
+
+    const releases: GitHubRelease[] = await response.json();
+
+    // Extract and normalize version numbers, then sort them in descending order
+    const versions = releases
+        .map(release => normalizeVersion(release.tag_name))
+        .sort((a, b) => {
+            const [aMajor, aMinor] = a.split('.').map(Number);
+            const [bMajor, bMinor] = b.split('.').map(Number);
+            if (bMajor !== aMajor) return bMajor - aMajor;
+            return bMinor - aMinor;
+        });
+
+    return versions;
+}
\ No newline at end of file
diff --git a/src/main.ts b/src/main.ts
index b022afa..beeaf33 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -1,6 +1,5 @@
 import axios from 'axios';
 import fs from 'fs';
-import path from 'path';
 import { promisify } from 'util';
 import { v4 as uuidv4 } from 'uuid';
 import { z } from 'zod';
@@ -83,7 +82,8 @@ export async function registerDataSource(registration: DataRegistration): Promis
  */
 async function fetchAttackDataFromGitHub(domain: string, version?: string): Promise<StixBundle> {
     let url = `${GITHUB_BASE_URL}/${domain}/`;
-    url += version ? `${domain}-${version}.json` : `${domain}.json`;
+    const normalizedVersion = version ? version.replace(/^v/, '') : version; // Remove leading 'v' if present
+    url += normalizedVersion ? `${domain}-${normalizedVersion}.json` : `${domain}.json`;
 
     try {
         const response = await axios.get<StixBundle>(url, {