docs(blog): add cosign Docker image verification instructions

Add steps for verifying Docker images with cosign to three security blog posts:
CI/CD v2, Security Townhall, and Security Update.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/my-website/blog/ci_cd_v2_improvements/index.md

@@ -27,6 +27,27 @@ Building on the roadmap from our [security incident](https://docs.litellm.ai/blo
 - Validation and release are separated into different repositories, making it harder for an attacker to reach release credentials.
 - Trusted Publishing for PyPI releases - this means no long-lived credentials are used to publish releases.
 - Immutable Docker release tags - this means no tampering of Docker release tags after they are published [Learn more](https://docs.docker.com/docker-hub/repos/manage/hub-images/immutable-tags/). Note: work for GHCR docker releases is planned as well.
+- Docker image signing with [Cosign](https://github.com/sigstore/cosign) - all release images are signed so users can independently verify they came from us.
+
+## Verify Docker image signatures
+
+All LiteLLM Docker images are signed with [cosign](https://docs.sigstore.dev/cosign/overview/). To verify the integrity of an image before deploying:
+
+```bash
+cosign verify \
+  --key https://raw.githubusercontent.com/BerriAI/litellm/<release-tag>/cosign.pub \
+  ghcr.io/berriai/litellm:<release-tag>
+```
+
+Replace `<release-tag>` with the version you are deploying (e.g. `v1.83.0-stable`).
+
+Expected output:
+
+```
+The following checks were performed on each of these signatures:
+  - The cosign claims were validated
+  - The signatures were verified against the specified public key
+```
 
 ## What's next
 

docs/my-website/blog/security_townhall_updates/index.md

@@ -145,6 +145,25 @@ This will ensure, your releases are safe, even when:
 
 We believe that [Cosign](https://github.com/sigstore/cosign) is a good fit for this, and have already begun working on it [PR](https://github.com/BerriAI/litellm/pull/24683).
 
+#### How to verify a Docker image with Cosign
+
+All LiteLLM Docker images are now signed with [cosign](https://docs.sigstore.dev/cosign/overview/). To verify the integrity of an image before deploying:
+
+```bash
+cosign verify \
+  --key https://raw.githubusercontent.com/BerriAI/litellm/<release-tag>/cosign.pub \
+  ghcr.io/berriai/litellm:<release-tag>
+```
+
+Replace `<release-tag>` with the version you are deploying (e.g. `v1.83.0-stable`).
+
+Expected output:
+
+```
+The following checks were performed on each of these signatures:
+  - The cosign claims were validated
+  - The signatures were verified against the specified public key
+```
 
 ### Avoid Compromised Packages
 

docs/my-website/blog/security_update_march_2026/index.md

@@ -708,6 +708,26 @@ The LiteLLM AI Gateway team has already taken the following steps:
 - Engaged Google's Mandiant security team to assist with forensic analysis of the build and publishing chain
 
 
+## Verify Docker image signatures
+
+All LiteLLM Docker images are signed with [cosign](https://docs.sigstore.dev/cosign/overview/). To verify the integrity of an image before deploying:
+
+```bash
+cosign verify \
+  --key https://raw.githubusercontent.com/BerriAI/litellm/<release-tag>/cosign.pub \
+  ghcr.io/berriai/litellm:<release-tag>
+```
+
+Replace `<release-tag>` with the version you are deploying (e.g. `v1.83.0-stable`).
+
+Expected output:
+
+```
+The following checks were performed on each of these signatures:
+  - The cosign claims were validated
+  - The signatures were verified against the specified public key
+```
+
 ## Verified safe versions
 
 We have audited every LiteLLM release published between v1.78.0 and v1.82.6 across both PyPI and Docker. Each artifact was verified by: