diff --git a/docs/calendar.md b/docs/calendar.md
index 389509be..401b5fae 100644
--- a/docs/calendar.md
+++ b/docs/calendar.md
@@ -70,7 +70,7 @@ Those on the free tier have access to 3 calendars, whereas paid subscribers can
 
 </div>
 
-Proton Calendar's web client has been [audited](https://proton.me/community/open-source#:~:text=Proton%20Calendar,-GitHub) by Securitum in 2021.
+In 2021, Securitum [audited](https://proton.me/community/open-source#:~:text=Proton%20Calendar) Proton Calendar's web client and provided a [letter of attestation](https://res.cloudinary.com/dbulfrlrz/images/v1714639870/wp-pme/letter-of-attestation-proton-calendar-20211109_3138998f9b/letter-of-attestation-proton-calendar-20211109_3138998f9b.pdf) for the Android app.
 
 ## Criteria