diff --git a/Cargo.lock b/Cargo.lock
index 245377ac..051370db 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -7085,6 +7085,7 @@ dependencies = [
  "indicatif",
  "lapin",
  "lazy_static",
+ "md-5",
  "mockito",
  "pipe-adapter-mail",
  "pipe-adapter-sdk",
diff --git a/Cargo.toml b/Cargo.toml
index c626b551..b4e72372 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -72,6 +72,8 @@ tokio-stream = "0.1.14"
 actix-http = "3.4.0"
 hmac = "0.12.1"
 sha2 = "0.10.8"
+# Gravatar avatar URLs for marketplace vendor profiles (helpers::gravatar).
+md-5 = "0.10"
 # Constant-time comparison for credential digests (helpers::agent_token).
 subtle = "2.6"
 sqlx-adapter = { version = "1.8.0", default-features = false, features = ["postgres", "runtime-tokio-native-tls"]}
diff --git a/migrations/20261029120000_null_non_gravatar_avatars.down.sql b/migrations/20261029120000_null_non_gravatar_avatars.down.sql
new file mode 100644
index 00000000..13e3c8e8
--- /dev/null
+++ b/migrations/20261029120000_null_non_gravatar_avatars.down.sql
@@ -0,0 +1 @@
+-- Data cleanup migration: cleared external avatar URLs cannot be restored.
diff --git a/migrations/20261029120000_null_non_gravatar_avatars.up.sql b/migrations/20261029120000_null_non_gravatar_avatars.up.sql
new file mode 100644
index 00000000..a92a5796
--- /dev/null
+++ b/migrations/20261029120000_null_non_gravatar_avatars.up.sql
@@ -0,0 +1,9 @@
+-- Vendor avatars are now derived from the account email via Gravatar
+-- (see helpers::gravatar and PATCH /mine/vendor-profile). Stored values
+-- from before that change may point at arbitrary external hosts, which
+-- must not reach public pages: clear every non-Gravatar avatar_url. The
+-- next profile save repopulates the column with the derived Gravatar URL.
+UPDATE marketplace_vendor_profile
+SET avatar_url = NULL
+WHERE avatar_url IS NOT NULL
+  AND avatar_url !~* '^https://([a-z0-9-]+\.)?gravatar\.com/';
diff --git a/src/helpers/gravatar.rs b/src/helpers/gravatar.rs
new file mode 100644
index 00000000..d3f7cdf6
--- /dev/null
+++ b/src/helpers/gravatar.rs
@@ -0,0 +1,78 @@
+use md5::{Digest, Md5};
+
+/// Gravatar avatar URL for a user's email, matching the platform convention in
+/// the user service (`app/oauth2_server/views.py`): MD5 of the trimmed,
+/// lowercased email. `d=identicon` serves a generated image when the email has
+/// no registered Gravatar, so the URL never 404s.
+pub fn gravatar_url(email: &str) -> String {
+    let hash = Md5::digest(email.trim().to_lowercase());
+    format!("https://www.gravatar.com/avatar/{hash:x}?s=230&d=identicon&r=pg")
+}
+
+/// Whether a URL is an https Gravatar avatar URL. Vendor profile avatars are
+/// restricted to this host so user-supplied values can never introduce
+/// arbitrary external images on public pages.
+pub fn is_gravatar_url(url: &str) -> bool {
+    match url.strip_prefix("https://") {
+        Some(rest) => {
+            let host = rest.split(['/', '?', '#']).next().unwrap_or("");
+            host.eq_ignore_ascii_case("gravatar.com")
+                || (host.len() > "gravatar.com".len()
+                    && host.to_ascii_lowercase().ends_with(".gravatar.com"))
+        }
+        None => false,
+    }
+}
+
+/// Whether a URL is a plain http(s) URL, rejecting `javascript:` and other
+/// schemes that must never reach an `href` attribute.
+pub fn is_http_url(url: &str) -> bool {
+    let lower = url.trim().to_ascii_lowercase();
+    lower.starts_with("https://") || lower.starts_with("http://")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn gravatar_url_hashes_trimmed_lowercase_email() {
+        // md5("test@example.com")
+        assert_eq!(
+            gravatar_url("  Test@Example.COM  "),
+            "https://www.gravatar.com/avatar/55502f40dc8b7c769880b10874abc9d0?s=230&d=identicon&r=pg"
+        );
+    }
+
+    #[test]
+    fn gravatar_url_accepts_any_email_shape() {
+        assert!(gravatar_url("").starts_with("https://www.gravatar.com/avatar/"));
+    }
+
+    #[test]
+    fn is_gravatar_url_accepts_gravatar_hosts_only() {
+        assert!(is_gravatar_url("https://www.gravatar.com/avatar/abc?s=230"));
+        assert!(is_gravatar_url("https://gravatar.com/avatar/abc"));
+        assert!(is_gravatar_url("https://secure.gravatar.com/avatar/abc"));
+        assert!(!is_gravatar_url("http://www.gravatar.com/avatar/abc"));
+        assert!(!is_gravatar_url(
+            "https://evil.example/gravatar.com/avatar/abc"
+        ));
+        assert!(!is_gravatar_url("https://gravatar.com.evil.example/abc"));
+        assert!(!is_gravatar_url("https://example.com/avatar.png"));
+        assert!(!is_gravatar_url("javascript:alert(1)"));
+        assert!(!is_gravatar_url("data:image/svg+xml,<svg/>"));
+        assert!(!is_gravatar_url(""));
+    }
+
+    #[test]
+    fn is_http_url_rejects_non_http_schemes() {
+        assert!(is_http_url("https://example.com"));
+        assert!(is_http_url("http://example.com"));
+        assert!(!is_http_url("javascript:alert(1)"));
+        assert!(!is_http_url("data:text/html,<script>"));
+        assert!(!is_http_url("vbscript:msgbox(1)"));
+        assert!(!is_http_url("example.com"));
+        assert!(!is_http_url(""));
+    }
+}
diff --git a/src/helpers/mod.rs b/src/helpers/mod.rs
index 3a6876aa..5ddad996 100644
--- a/src/helpers/mod.rs
+++ b/src/helpers/mod.rs
@@ -28,6 +28,7 @@ pub(crate) mod compressor;
 pub mod dockerhub;
 pub mod env_path;
 pub mod fs;
+pub mod gravatar;
 pub(crate) mod ip;
 pub mod stacker_labels;
 
diff --git a/src/routes/marketplace/creator.rs b/src/routes/marketplace/creator.rs
index c87e57bf..b4c3ea0f 100644
--- a/src/routes/marketplace/creator.rs
+++ b/src/routes/marketplace/creator.rs
@@ -1695,7 +1695,6 @@ pub struct UpdateVendorPublicProfileRequest {
     pub public_slug: Option<String>,
     pub display_name: Option<String>,
     pub bio: Option<String>,
-    pub avatar_url: Option<String>,
     pub website_url: Option<String>,
 }
 
@@ -1722,13 +1721,24 @@ pub async fn update_vendor_public_profile_handler(
         }
     }
 
+    if let Some(ref website_url) = req.website_url {
+        if !website_url.is_empty() && !crate::helpers::gravatar::is_http_url(website_url) {
+            return Err(JsonResponse::<serde_json::Value>::build()
+                .bad_request("website_url must be an http(s) URL"));
+        }
+    }
+
+    // Avatar is always derived from the account email via Gravatar; the
+    // client cannot supply an arbitrary external image URL.
+    let avatar_url = crate::helpers::gravatar::gravatar_url(&user.email);
+
     db::marketplace::update_vendor_public_profile(
         pg_pool.get_ref(),
         &user.id,
         req.public_slug.as_deref(),
         req.display_name.as_deref(),
         req.bio.as_deref(),
-        req.avatar_url.as_deref(),
+        Some(&avatar_url),
         req.website_url.as_deref(),
     )
     .await
diff --git a/tests/marketplace_creator_self_vendor_profile.rs b/tests/marketplace_creator_self_vendor_profile.rs
index 68a580d8..24edfc19 100644
--- a/tests/marketplace_creator_self_vendor_profile.rs
+++ b/tests/marketplace_creator_self_vendor_profile.rs
@@ -198,8 +198,10 @@ async fn creator_patch_vendor_public_profile_creates_profile_when_missing() {
     assert_eq!("acme-cloud", profile["public_slug"]);
     assert_eq!("Acme Cloud", profile["display_name"]);
     assert_eq!("We build stacks.", profile["bio"]);
+    // Avatar is derived from the account email via Gravatar; the
+    // client-supplied avatar_url must never be stored.
     assert_eq!(
-        "https://acme-cloud.example.com/avatar.png",
+        "https://www.gravatar.com/avatar/55502f40dc8b7c769880b10874abc9d0?s=230&d=identicon&r=pg",
         profile["avatar_url"]
     );
     assert_eq!("https://acme-cloud.example.com", profile["website_url"]);
@@ -228,7 +230,8 @@ async fn creator_patch_vendor_public_profile_updates_existing_profile() {
     .await
     .expect("Failed to seed vendor profile");
 
-    // Update only display_name and bio — slug and URLs should be preserved via COALESCE
+    // Update only display_name and bio — slug and website_url are preserved
+    // via COALESCE, while avatar_url is re-derived from the account email.
     let response = reqwest::Client::new()
         .patch(format!("{}/api/templates/mine/vendor-profile", app.address))
         .bearer_auth(USER_TOKEN)
@@ -259,7 +262,11 @@ async fn creator_patch_vendor_public_profile_updates_existing_profile() {
     assert_eq!("old-slug", profile["public_slug"]);
     assert_eq!("New Name", profile["display_name"]);
     assert_eq!("New bio", profile["bio"]);
-    assert_eq!("https://old.example.com/avatar.png", profile["avatar_url"]);
+    // The legacy external avatar is replaced with the derived Gravatar URL.
+    assert_eq!(
+        "https://www.gravatar.com/avatar/55502f40dc8b7c769880b10874abc9d0?s=230&d=identicon&r=pg",
+        profile["avatar_url"]
+    );
     assert_eq!("https://old.example.com", profile["website_url"]);
 }
 
@@ -283,6 +290,104 @@ async fn creator_patch_vendor_public_profile_rejects_invalid_slug() {
     assert_eq!(StatusCode::BAD_REQUEST, response.status());
 }
 
+#[tokio::test]
+async fn creator_patch_vendor_public_profile_ignores_client_supplied_avatar_url() {
+    let app = match common::spawn_app().await {
+        Some(app) => app,
+        None => return,
+    };
+
+    // Regression: the client-supplied avatar_url must never be stored or
+    // served — vendor avatars are always derived via Gravatar from the
+    // account email so public pages cannot load arbitrary external images.
+    let response = reqwest::Client::new()
+        .patch(format!("{}/api/templates/mine/vendor-profile", app.address))
+        .bearer_auth(USER_TOKEN)
+        .json(&json!({
+            "display_name": "Acme Cloud",
+            "avatar_url": "https://evil.example/track.png",
+            "public_slug": "acme-cloud"
+        }))
+        .send()
+        .await
+        .expect("Failed to PATCH vendor public profile");
+
+    assert_eq!(StatusCode::OK, response.status());
+
+    let get_response = reqwest::Client::new()
+        .get(format!("{}/api/templates/mine/vendor-profile", app.address))
+        .bearer_auth(USER_TOKEN)
+        .send()
+        .await
+        .expect("Failed to GET self vendor profile after PATCH");
+
+    let body: Value = get_response
+        .json()
+        .await
+        .expect("response should be valid JSON");
+
+    let profile = &body["item"]["vendor_profile"];
+    assert_eq!(
+        "https://www.gravatar.com/avatar/55502f40dc8b7c769880b10874abc9d0?s=230&d=identicon&r=pg",
+        profile["avatar_url"]
+    );
+
+    // The same must hold on the public vendor page.
+    let public_response = reqwest::Client::new()
+        .get(format!("{}/api/vendors/acme-cloud", app.address))
+        .send()
+        .await
+        .expect("Failed to GET public vendor profile");
+
+    assert_eq!(StatusCode::OK, public_response.status());
+
+    let public_body: Value = public_response
+        .json()
+        .await
+        .expect("public response should be valid JSON");
+
+    assert_eq!(
+        "https://www.gravatar.com/avatar/55502f40dc8b7c769880b10874abc9d0?s=230&d=identicon&r=pg",
+        public_body["item"]["vendor"]["avatar_url"]
+    );
+}
+
+#[tokio::test]
+async fn creator_patch_vendor_public_profile_rejects_non_http_website_url() {
+    let app = match common::spawn_app().await {
+        Some(app) => app,
+        None => return,
+    };
+
+    // website_url is rendered into an <a href> on the public page, so only
+    // http(s) URLs may be stored.
+    for malicious in ["javascript:alert(1)", "data:text/html,<script>", "vbscript:msgbox(1)"] {
+        let response = reqwest::Client::new()
+            .patch(format!("{}/api/templates/mine/vendor-profile", app.address))
+            .bearer_auth(USER_TOKEN)
+            .json(&json!({
+                "website_url": malicious
+            }))
+            .send()
+            .await
+            .expect("Failed to PATCH vendor public profile");
+
+        assert_eq!(StatusCode::BAD_REQUEST, response.status(), "url: {malicious}");
+    }
+
+    let response = reqwest::Client::new()
+        .patch(format!("{}/api/templates/mine/vendor-profile", app.address))
+        .bearer_auth(USER_TOKEN)
+        .json(&json!({
+            "website_url": "https://acme-cloud.example.com"
+        }))
+        .send()
+        .await
+        .expect("Failed to PATCH vendor public profile");
+
+    assert_eq!(StatusCode::OK, response.status());
+}
+
 #[tokio::test]
 async fn creator_patch_vendor_public_profile_requires_authentication() {
     let app = match common::spawn_app().await {