diff --git a/mclib/src/repos/CurseForgeRepository.ts b/mclib/src/repos/CurseForgeRepository.ts
index 7f661d8..4083066 100644
--- a/mclib/src/repos/CurseForgeRepository.ts
+++ b/mclib/src/repos/CurseForgeRepository.ts
@@ -2,6 +2,7 @@ import type { IRepository } from "./IRepository";
 import { RawModRepoRelease, ModRepositoryName, ModLoader, ModRepoMetadata, MCVersion } from "..";
 import { cf_fingerprint } from 'cf-fingerprint';
 import { logger } from "../logger";
+import { validateParam } from "../utils";
 
 // Translation map for Curseforge modloader IDs
 // Source: https://docs.curseforge.com/rest-api/#tocS_ModLoaderType
@@ -25,6 +26,8 @@ export class CurseForgeRepository implements IRepository {
     }
 
     async getModReleases(modId: string): Promise<RawModRepoRelease[]> {
+        validateParam(modId);
+
         const modInfo = await this.fetchModInfo(Number(modId));
         if (!modInfo || !modInfo.latestFilesIndexes) return [];
 
@@ -47,6 +50,9 @@ export class CurseForgeRepository implements IRepository {
     }
 
     async searchMods(query: string, maxResults: number): Promise<ModRepoMetadata[]> {
+        validateParam(query);
+        validateParam(maxResults.toString());
+
         type Data = {
             data: {
                 id: number;
@@ -70,7 +76,7 @@ export class CurseForgeRepository implements IRepository {
             pageSize: maxResults.toString(),
             sortField: "1",
             sortOrder: "desc",
-            searchFilter: query
+            searchFilter: query,
         }));
         if (!resp.ok) throw new Error("Failed to fetch search results from CurseForge");
         const jsonResp: Data = (await resp.json());
@@ -87,12 +93,16 @@ export class CurseForgeRepository implements IRepository {
     }
 
     private async fetchModInfo(modId: number): Promise<ModInfoData | null> {
+        validateParam(modId.toString());
+
         const modResp = await this.fetchClient(`${CurseForgeRepository.BASE_URL}/mods/${modId}`);
         if (!modResp.ok) return null;
         return (await modResp.json()).data as ModInfoData;
     }
 
     async getByDataHash(hash: string): Promise<ModRepoMetadata | null> {
+        validateParam(hash);
+
         // Use the CurseForge API to get file info by fingerprint
         const resp = await this.fetchClient(`${CurseForgeRepository.BASE_URL}/fingerprints`, {
             method: 'POST',
diff --git a/mclib/src/repos/ModrinthRepository.ts b/mclib/src/repos/ModrinthRepository.ts
index 5554cce..743d3a2 100644
--- a/mclib/src/repos/ModrinthRepository.ts
+++ b/mclib/src/repos/ModrinthRepository.ts
@@ -1,13 +1,14 @@
 import type { IRepository } from "./IRepository";
 import { ModRepositoryName, ModRepoMetadata, ModLoaderUtil, RawModRepoRelease } from "..";
+import { validateParam } from "../utils";
 
 // https://devblogs.microsoft.com/typescript/announcing-typescript-5-9-rc/#notable-behavioral-changes
 function toArrayBuffer(buf: ArrayBufferLike): ArrayBuffer {
-  if (buf instanceof ArrayBuffer) return buf;
-  // SharedArrayBuffer → copy into a new ArrayBuffer
-  const copy = new Uint8Array(buf.byteLength);
-  copy.set(new Uint8Array(buf));
-  return copy.buffer;
+    if (buf instanceof ArrayBuffer) return buf;
+    // SharedArrayBuffer → copy into a new ArrayBuffer
+    const copy = new Uint8Array(buf.byteLength);
+    copy.set(new Uint8Array(buf));
+    return copy.buffer;
 }
 
 
@@ -20,6 +21,8 @@ export class ModrinthRepository implements IRepository {
     }
 
     async getModReleases(modId: string): Promise<RawModRepoRelease[]> {
+        validateParam(modId);
+
         type Data = Array<{
             game_versions: string[];
             version_number: string;
@@ -49,6 +52,9 @@ export class ModrinthRepository implements IRepository {
     }
 
     async searchMods(query: string, maxResults: number): Promise<ModRepoMetadata[]> {
+        validateParam(query);
+        validateParam(maxResults.toString());
+
         type Data = {
             hits: Array<{
                 slug: string;
@@ -74,6 +80,8 @@ export class ModrinthRepository implements IRepository {
     }
 
     async getByDataHash(hash: string): Promise<ModRepoMetadata | null> {
+        validateParam(hash);
+
         // Get version info using the hash
         const versionResp = await this.fetchClient(`https://api.modrinth.com/v2/version_file/${hash}`);
         if (!versionResp.ok) return null;
diff --git a/mclib/src/utils.ts b/mclib/src/utils.ts
new file mode 100644
index 0000000..caf3f3d
--- /dev/null
+++ b/mclib/src/utils.ts
@@ -0,0 +1,5 @@
+export function validateParam(s: string) {
+    if (!/^[a-zA-Z0-9]{0,64}$/.test(s)) {
+        throw new Error('Invalid parameter: must be 0-64 alphanumeric characters');
+    }
+}