diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index ae0f708..dbcc8bd 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -1,35 +1,40 @@
-# To get started with Dependabot version updates, you'll need to specify which
-# package ecosystems to update and where the package manifests are located.
-# https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#versioning-strategy
+# Dependabot: security updates only (no version-update PRs).
+# Grouped security PRs open weekly on Tuesday morning (Europe/Bucharest).
+# Auto-merge: .github/workflows/dependabot-auto-merge.yml (on PR + Tuesday cron).
+# https://docs.github.com/en/code-security/dependabot/dependabot-security-updates
 
 version: 2
 updates:
-  # Keep the Cargo dependencies up to date
   - package-ecosystem: "cargo"
     directory: "/"
     schedule:
-      interval: "weekly"
-      day: "monday"
-    target-branch: "main"
+      interval: weekly
+      day: tuesday
+      time: "06:00"
+      timezone: Europe/Bucharest
+    open-pull-requests-limit: 0
     labels:
+      - "dependabot-security"
       - "rust dependencies"
     groups:
-      cargo:
-        applies-to: version-updates
+      cargo-security:
+        applies-to: security-updates
         patterns:
           - "*"
 
-  # Keep the Github Actions dependencies up to date
   - package-ecosystem: "github-actions"
     directory: "/"
     schedule:
-      interval: "weekly"
-      day: "monday"
-    target-branch: "main"
+      interval: weekly
+      day: tuesday
+      time: "06:00"
+      timezone: Europe/Bucharest
+    open-pull-requests-limit: 0
     labels:
+      - "dependabot-security"
       - "github dependencies"
     groups:
-      github:
-        applies-to: version-updates
+      github-actions-security:
+        applies-to: security-updates
         patterns:
           - "*"
diff --git a/.github/workflows/auto_assign_ci.yaml b/.github/workflows/auto_assign_ci.yaml
index 0e6c515..59aa47c 100644
--- a/.github/workflows/auto_assign_ci.yaml
+++ b/.github/workflows/auto_assign_ci.yaml
@@ -1,4 +1,5 @@
 name: Auto Assign
+# Audit 2026-10-14: pull_request_target — do not checkout the PR head here; configuration-path only.
 
 on:
   pull_request_target:
@@ -16,6 +17,6 @@ jobs:
     name: Auto assign (me only)
     runs-on: ubuntu-latest
     steps:
-      - uses: kentaro-m/auto-assign-action@v2.0.2
+      - uses: kentaro-m/auto-assign-action@0a2c53d3721e4c5cfcce6afd4014aecc337979f6 # v2.0.2
         with:
           configuration-path: ".github/auto_assign.yml"
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index 06307a8..9acb64c 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -61,7 +61,7 @@ jobs:
         # your codebase is analyzed, see https://docs.github.com/en/code-security/code-scanning/creating-an-advanced-setup-for-code-scanning/codeql-code-scanning-for-compiled-languages
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v7
+      uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
 
     # Add any setup steps before running the `github/codeql-action/init` action.
     # This includes steps like installing compilers or runtimes (`actions/setup-node`
@@ -71,7 +71,7 @@ jobs:
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
-      uses: github/codeql-action/init@v4.37.8
+      uses: github/codeql-action/init@db488ddef3bf6cb639b32c2e9a7c0a7ea8271d28 # v4.37.8
       with:
         languages: ${{ matrix.language }}
         build-mode: ${{ matrix.build-mode }}
@@ -100,6 +100,6 @@ jobs:
         exit 1
 
     - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@v4.37.8
+      uses: github/codeql-action/analyze@db488ddef3bf6cb639b32c2e9a7c0a7ea8271d28 # v4.37.8
       with:
         category: "/language:${{matrix.language}}"
diff --git a/.github/workflows/dependabot-auto-merge.yml b/.github/workflows/dependabot-auto-merge.yml
new file mode 100644
index 0000000..138a59d
--- /dev/null
+++ b/.github/workflows/dependabot-auto-merge.yml
@@ -0,0 +1,50 @@
+name: Dependabot security auto-merge
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened]
+  schedule:
+    - cron: "0 6 * * 2"
+      timezone: Europe/Bucharest
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  approve-and-queue-merge:
+    runs-on: ubuntu-latest
+    if: >-
+      github.event_name == 'pull_request'
+      && github.event.pull_request.user.login == 'dependabot[bot]'
+    steps:
+      - name: Approve Dependabot pull request
+        run: gh pr review --approve "$PR_URL"
+        env:
+          PR_URL: ${{ github.event.pull_request.html_url }}
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Enable auto-merge when checks pass
+        run: gh pr merge --auto --merge "$PR_URL"
+        env:
+          PR_URL: ${{ github.event.pull_request.html_url }}
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+  weekly-merge-ready:
+    runs-on: ubuntu-latest
+    if: github.event_name == 'schedule'
+    steps:
+      - name: Approve and queue merge for open Dependabot PRs
+        run: |
+          set -euo pipefail
+          mapfile -t urls < <(gh pr list --author app/dependabot --state open --json url --jq '.[].url')
+          if [ "${#urls[@]}" -eq 0 ]; then
+            echo "No open Dependabot pull requests."
+            exit 0
+          fi
+          for url in "${urls[@]}"; do
+            gh pr review --approve "$url" || true
+            gh pr merge --auto --merge "$url" || true
+          done
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index c72a2ad..799635c 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -13,15 +13,28 @@ permissions:
 
 jobs:
   validate-tag:
+    outputs:
+      tag_sha: ${{ steps.tag_sha.outputs.sha }}
     name: Validate tag
     runs-on: ubuntu-latest
     steps:
+      - name: Validate tag input
+        env:
+          TAG: ${{ github.event.inputs.tag }}
+        run: |
+          re='^v?[0-9]+\.[0-9]+\.[0-9]+([.+-][0-9A-Za-z.-]+)?$'
+          if [[ ! "$TAG" =~ $re ]]; then
+            echo "Error: the tag input must be a release tag such as v1.2.3."
+            exit 1
+          fi
+
       - name: Checkout
-        uses: actions/checkout@v7
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           fetch-depth: 0
-          ref: ${{ github.event.inputs.tag }}
+          ref: refs/tags/${{ github.event.inputs.tag }}
 
+          persist-credentials: false
       - name: Verify tag and crate version
         run: |
           TAG="${{ github.event.inputs.tag }}"
@@ -29,7 +42,7 @@ jobs:
             echo "Error: Tag is required."
             exit 1
           fi
-          if ! git rev-parse "$TAG" >/dev/null 2>&1; then
+          if ! git rev-parse -q --verify "refs/tags/$TAG" >/dev/null; then
             echo "Error: Tag '$TAG' does not exist."
             exit 1
           fi
@@ -43,7 +56,14 @@ jobs:
             echo "Error: Cargo.toml version ($PKG_VERSION) does not match tag ($TAG)."
             exit 1
           fi
-          echo "Publishing tag: $TAG (zero-bounce@$PKG_VERSION)"
+          
+      - name: Record tag commit SHA
+        id: tag_sha
+        env:
+          TAG: ${{ github.event.inputs.tag }}
+        run: |
+          SHA=$(git rev-parse "refs/tags/$TAG^{commit}")
+          echo "sha=$SHA" >> "$GITHUB_OUTPUT"
 
   test:
     name: Test
@@ -52,19 +72,19 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout tag
-        uses: actions/checkout@v7
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
-          ref: ${{ github.event.inputs.tag }}
-
+          ref: ${{ needs.validate-tag.outputs.tag_sha }}
+          persist-credentials: false
       - name: Set up Rust
-        uses: dtolnay/rust-toolchain@stable
+        uses: dtolnay/rust-toolchain@686976e191b89faba57d3206551f0f330d8cb249 # stable
 
       - name: Run tests
         run: cargo test --no-fail-fast
 
   publish:
     name: Publish to crates.io
-    needs: [test]
+    needs: [validate-tag, test]
     if: ${{ !cancelled() && !failure() }}
     runs-on: ubuntu-latest
     environment: release
@@ -73,15 +93,15 @@ jobs:
       contents: read
     steps:
       - name: Checkout tag
-        uses: actions/checkout@v7
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
-          ref: ${{ github.event.inputs.tag }}
-
+          ref: ${{ needs.validate-tag.outputs.tag_sha }}
+          persist-credentials: false
       - name: Set up Rust
-        uses: dtolnay/rust-toolchain@stable
+        uses: dtolnay/rust-toolchain@686976e191b89faba57d3206551f0f330d8cb249 # stable
 
       - name: Authenticate with crates.io
-        uses: rust-lang/crates-io-auth-action@v1
+        uses: rust-lang/crates-io-auth-action@c6f97d42243bad5fab37ca0427f495c86d5b1a18 # v1
         id: auth
 
       - name: Publish to crates.io
@@ -91,28 +111,29 @@ jobs:
 
   release:
     name: Create GitHub Release
-    needs: [publish]
+    needs: [validate-tag, publish]
     if: ${{ !cancelled() && !failure() }}
     runs-on: ubuntu-latest
     permissions:
       contents: write
     steps:
       - name: Checkout
-        uses: actions/checkout@v7
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
-          ref: ${{ github.event.inputs.tag }}
+          ref: ${{ needs.validate-tag.outputs.tag_sha }}
           fetch-depth: 0
 
+          persist-credentials: false
       - name: Create release if missing
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: |
           TAG="${{ github.event.inputs.tag }}"
-          if gh release view "$TAG" --repo "${{ github.repository }}" >/dev/null 2>&1; then
+          if gh release view "$TAG" --repo "$GITHUB_REPOSITORY" >/dev/null 2>&1; then
             echo "Release $TAG already exists, skipping."
           else
             gh release create "$TAG" \
-              --repo "${{ github.repository }}" \
+              --repo "$GITHUB_REPOSITORY" \
               --title "$TAG" \
               --generate-notes
           fi
diff --git a/.github/workflows/sdk_ci.yml b/.github/workflows/sdk_ci.yml
index 4cf671e..f8212e6 100644
--- a/.github/workflows/sdk_ci.yml
+++ b/.github/workflows/sdk_ci.yml
@@ -15,10 +15,12 @@ jobs:
     name: Test
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
 
       - name: Set up Rust
-        uses: dtolnay/rust-toolchain@stable
+        uses: dtolnay/rust-toolchain@686976e191b89faba57d3206551f0f330d8cb249 # stable
         with:
           components: rustfmt, clippy
 
diff --git a/Dockerfile b/Dockerfile
index 9bd67f6..ba3c06a 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -7,4 +7,7 @@ WORKDIR /app
 COPY . .
 
 # Full test suite (unit + integration; network allowed in container)
+
+USER 65532:65532
+
 CMD ["cargo", "test", "--no-fail-fast"]
diff --git a/src/api/bulk.rs b/src/api/bulk.rs
index 675c220..a711423 100644
--- a/src/api/bulk.rs
+++ b/src/api/bulk.rs
@@ -31,12 +31,6 @@ impl ZeroBounce {
         let response_ok = response.status().is_success();
         let response_content = response.text()?;
 
-        // Debug: Print raw response to examine structure in debug mode
-        #[cfg(debug_assertions)]
-        {
-            eprintln!("Raw API response: {}", response_content);
-        }
-
         if !response_ok {
             return Err(ZBError::ExplicitError(response_content));
         }
@@ -93,12 +87,10 @@ impl ZeroBounce {
             .to_string();
 
         let body_bytes = response.bytes()?;
-        let body_str = String::from_utf8_lossy(&body_bytes).into_owned();
-
-        #[cfg(debug_assertions)]
-        if !status.is_success() || should_treat_get_file_body_as_error(&body_str, &content_type) {
-            eprintln!("Raw API response: {}", body_str);
+        if body_bytes.len() > crate::utility::MAX_GETFILE_BYTES {
+            return Err(ZBError::ExplicitError("getfile response exceeds size limit".into()));
         }
+        let body_str = String::from_utf8_lossy(&body_bytes).into_owned();
 
         if !status.is_success() {
             let msg = if body_str.trim_start().starts_with('{') {
diff --git a/src/api/validation.rs b/src/api/validation.rs
index e3ea75b..d85a5a0 100644
--- a/src/api/validation.rs
+++ b/src/api/validation.rs
@@ -90,11 +90,6 @@ impl ZeroBounce {
         let response_content = response.text()?;
 
         // Debug: Print raw response to examine structure in debug mode
-        #[cfg(debug_assertions)]
-        {
-            eprintln!("Raw API response: {}", response_content);
-        }
-
         if !response_ok {
             return Err(ZBError::ExplicitError(response_content));
         }
diff --git a/src/lib.rs b/src/lib.rs
index 2daa096..86a493b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -112,6 +112,9 @@ impl ZeroBounce {
 
         let response_ok = response.status().is_success();
         let response_content = response.text()?;
+        if response_content.len() > utility::MAX_JSON_RESPONSE_BYTES {
+            return Err(ZBError::ExplicitError("response body exceeds size limit".into()));
+        }
 
         if !response_ok {
             return Err(ZBError::ExplicitError(response_content));
@@ -126,11 +129,16 @@ fn require_https_url(url: String) -> String {
     if lower.starts_with("https://") {
         return url;
     }
-    // mockito and local tests use loopback HTTP
-    if lower.starts_with("http://127.0.0.1")
-        || lower.starts_with("http://localhost")
-        || lower.starts_with("http://[::1]")
-    {
+    let is_loopback_http = reqwest::Url::parse(&url)
+        .map(|parsed| {
+            parsed.scheme() == "http"
+                && matches!(
+                    parsed.host_str(),
+                    Some("127.0.0.1") | Some("localhost") | Some("[::1]")
+                )
+        })
+        .unwrap_or(false);
+    if is_loopback_http {
         return url;
     }
     panic!("base_url must be an https:// URL");
@@ -161,4 +169,16 @@ mod security_tests {
     fn rejects_remote_http() {
         require_https_url("http://evil.example/v2/".to_string());
     }
+
+    #[test]
+    #[should_panic(expected = "https://")]
+    fn rejects_loopback_lookalike_host() {
+        require_https_url("http://localhost.evil.example/v2/".to_string());
+    }
+
+    #[test]
+    #[should_panic(expected = "https://")]
+    fn rejects_loopback_userinfo_trick() {
+        require_https_url("http://127.0.0.1@evil.example/v2/".to_string());
+    }
 }
diff --git a/src/utility/mod.rs b/src/utility/mod.rs
index be59591..9f6f1a3 100644
--- a/src/utility/mod.rs
+++ b/src/utility/mod.rs
@@ -8,6 +8,10 @@ pub use bulk_get_file::{format_get_file_error_message, get_file_json_indicates_e
 
 pub const CONTENT_TYPE_JSON: &str = "application/json";
 pub const CONTENT_TYPE_STREAM: &str = "application/octet-stream";
+/// Cap JSON API responses so error pages cannot exhaust memory (RS-05).
+pub const MAX_JSON_RESPONSE_BYTES: usize = 16 * 1024 * 1024;
+/// Cap bulk getfile downloads (still large enough for typical CSV exports).
+pub const MAX_GETFILE_BYTES: usize = 256 * 1024 * 1024;
 
 /// Enum representing the available API base URLs
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -116,8 +120,29 @@ impl ZBError {
 //
 // This automatic conversion is expected when using the client
 // and issuing http requests.
+fn redact_api_key(url: &mut reqwest::Url) {
+    if !url.query_pairs().any(|(key, _)| key == "api_key") {
+        return;
+    }
+    let pairs: Vec<(String, String)> = url
+        .query_pairs()
+        .map(|(key, value)| {
+            let value = if key == "api_key" {
+                "REDACTED".to_string()
+            } else {
+                value.into_owned()
+            };
+            (key.into_owned(), value)
+        })
+        .collect();
+    url.query_pairs_mut().clear().extend_pairs(pairs);
+}
+
 impl From<reqwest::Error> for ZBError {
-    fn from(value: reqwest::Error) -> ZBError {
+    fn from(mut value: reqwest::Error) -> ZBError {
+        if let Some(url) = value.url_mut() {
+            redact_api_key(url);
+        }
         ZBError::RequestError(value)
     }
 }