WhatsApp and Telegram are popular secure messaging apps that feature end-to-end encryption to keep messages safe. Even still, the apps have a glaring backdoor that could allow attackers to alter media files sent through the apps. Both apps can store media to publicly accessible file directories, which leaves them vulnerable to manipulation.
https://www.notebookcheck.net/Researchers-at-Symantec-discover-media-file-vulnerability-in-WhatsApp-and-Telegram.427741.0.html