"A Signal spokesman said the Pentagon memo is not about the messaging app's level of security, but rather that users of the service should be aware of what are known as "phishing attacks." That's when hackers try to gain access to sensitive information through impersonation or other deceptive tricks.
"Once we learned that Signal users were being targeted and how they were being targeted, we introduced additional safeguards and in-app warnings to help protect people from falling victim to phishing attacks. This work was completed months ago," said Signal spokesman Jun Harada.
The March 18, 2025, Pentagon memo adds, "Please note: third party messaging apps (e.g. Signal) are permitted by policy for unclassified accountability/recall exercises but are NOT approved to process or store nonpublic unclassified information.""
https://www.npr.org/2025/03/25/nx-s1-5339801/pentagon-email-signal-vulnerability