Medium Severity

Link: Unicode character obfuscation in display name with base64-encoded URL fragment

Labels

Credential Phishing
Evasion
Social engineering
URL analysis
Sender analysis
Content analysis

Description

Detects inbound messages where the sender's display name contains Unicode format characters (such as word joiners or invisible separators) interspersed between letters to evade text-based detection. These messages carry links whose URL fragments are unusually long (over 100 characters) and match a base64url-encoded pattern, a technique used to smuggle encoded payloads past URL scanners.

References

No references.

Sublime Security
Created Aug 3rd, 2026 • Last updated Aug 3rd, 2026
Feed Source
Sublime Core Feed
Source
GitHub
type.inbound
and regex.icontains(sender.display_name, '[a-z]\p{Cf}+[a-z]')
and any(body.links,
        length(.href_url.fragment) > 100
        and regex.contains(.href_url.fragment, '^[A-Za-z0-9_-]+={0,2}$')
)
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