Attachment: HTML smuggling with RC4 decryption

calendar Aug 21, 2023  ยท
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Potential HTML smuggling. The RC4 algorithm is used within inline JavaScript to decrypt the payload on-the-fly.

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 1name: "Attachment: HTML smuggling with RC4 decryption"
 2description: |
 3  Potential HTML smuggling.
 4  The RC4 algorithm is used within inline JavaScript to decrypt the payload on-the-fly.  
 5references:
 6  - "https://delivr.to/payloads?id=0dcec496-0130-465c-bf3d-c9714e17d4d4"
 7  - "https://playground.sublimesecurity.com?id=6b219754-2b0b-47c3-ba53-ec080d946499"
 8type: "rule"
 9severity: "high"
10source: |
11  type.inbound
12  and any(attachments,
13          (
14            .file_extension in~ ("html", "htm", "shtml", "dhtml")
15            or .file_extension in~ $file_extensions_common_archives
16            or .file_type == "html"
17          )
18          and any(file.explode(.),
19                  any(.scan.strings.strings, strings.ilike(., "*?[(?[?]+?[?])%256]*"))
20          )
21  )  
22attack_types:
23  - "Credential Phishing"
24  - "Malware/Ransomware"
25tactics_and_techniques:
26  - "Encryption"
27  - "Evasion"
28  - "HTML smuggling"
29  - "Scripting"
30detection_methods:
31  - "Archive analysis"
32  - "Content analysis"
33  - "File analysis"
34  - "HTML analysis"
35  - "Javascript analysis"
36id: "3a46d765-4b27-5026-9b8e-043e3817854b"
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