diff --git a/frontend/src/services/nizkctf/github.js b/frontend/src/services/nizkctf/github.js
index 1e7fc4a..df6f2c4 100644
--- a/frontend/src/services/nizkctf/github.js
+++ b/frontend/src/services/nizkctf/github.js
@@ -78,12 +78,14 @@ export default class GitHub {
     };
   }
 
-  async listPullRequests(repoName, username, state) {
+  async listPullRequests(repoName, state, filter, username = null) {
     const status = state === "opened" ? "open" : state;
 
     const { owner, repo } = repoNameHandler(repoName);
 
-    const query = `is:pr+repo:${owner}/${repo}+author:${username}+state:${status}`;
+    const query = filter
+      ? `${filter}+is:pr+repo:${owner}/${repo}+state:${status}`
+      : `is:pr+repo:${owner}/${repo}+author:${username}+state:${status}`;
 
     const { data } = await this.octokit.search.issuesAndPullRequests({
       q: query
diff --git a/frontend/src/services/nizkctf/gitlab.js b/frontend/src/services/nizkctf/gitlab.js
index 2c268a1..deb0bf0 100644
--- a/frontend/src/services/nizkctf/gitlab.js
+++ b/frontend/src/services/nizkctf/gitlab.js
@@ -86,6 +86,7 @@ export default class GitLab {
     };
   }
   async listPullRequests(projectId, authorUsername, state) {
+    // TODO implements filter
     const response = await this.api.MergeRequests.all({
       projectId,
       authorUsername,
diff --git a/frontend/src/services/nizkctf/index.js b/frontend/src/services/nizkctf/index.js
index 9a6d33c..27bb2a6 100644
--- a/frontend/src/services/nizkctf/index.js
+++ b/frontend/src/services/nizkctf/index.js
@@ -57,7 +57,19 @@ export default class NIZKCTF {
     const proof = await this._createProof(challenge, keys.privateKey);
 
     const path = getTeamPath(this.team.name);
-    const message = `Proof: found flag for ${challenge.id}`;
+    const message = `Proof: found flag for ${challenge.id} - ${path}`;
+
+    const list = await this.api.listPullRequests(
+      this.upstream,
+      "opened",
+      `${message}:in:title`
+    );
+
+    if (list.length > 0) {
+      throw new Error(
+        "Your team has already sent this flag and it is in the bot's processing queue"
+      );
+    }
 
     const newProof = Buffer.from(proof).toString("base64");