Stored XSS in app.lemlist.com

## Summary: [add summary of the vulnerability] ## Steps To Reproduce: - Go to Company > Buddies-to-Be > Custom variables - Add malicious code: `" onmouseover="confirm(document.domain)" a="` {F915718} - Go to Company > Messages > Blank email - In the WYSIWYG editor select `Custom variables` - Malicious code executed {F915719} ## Impact With this vulnerability, an attacker can for example steal users cookies or redirect users on malicious website.