Suspicious Office 365 app authorization (OAuth) link

calendar Jun 5, 2026  ·
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Message contains a suspicious Office 365 app authorization (OAuth) link. The app may be compromised or was stood up for malicious purposes. Once the app has been authorized, the attacker will have read or write permissions to the user's Office 365 account.

Sublime rule (View on GitHub)

 1name: "Suspicious Office 365 app authorization (OAuth) link"
 2description: |
 3  Message contains a suspicious Office 365 app authorization (OAuth) link. The app may be compromised or 
 4  was stood up for malicious purposes. Once the app has been authorized, the attacker will have 
 5  read or write permissions to the user's Office 365 account.  
 6references:
 7  - "https://info.phishlabs.com/blog/office-365-phishing-uses-malicious-app-persist-password-reset"
 8type: "rule"
 9severity: "high"
10source: |
11  type.inbound
12  and (
13    // links in email body
14    any(body.links,
15        .href_url.domain.domain == 'login.microsoftonline.com'
16        and (
17          strings.ilike(.href_url.query_params,
18                        '*offline_access*',
19                        '*.readwrite*',
20                        '*.read*',
21                        '*ctx=*',
22                        '*prompt=none*'
23          )
24          or (
25            strings.icontains(.href_url.path, '/common/reprocess')
26            and strings.icontains(.href_url.query_params, 'ctx=')
27            and strings.icontains(.href_url.query_params, 'sessionId=')
28          )
29        )
30    )
31    // links in PDF, HTML, DOCX and PPTX attachments
32    or any(filter(attachments, .file_type in ("pdf", "html", "docx", "pptx")),
33           any(file.explode(.),
34               any(.scan.url.urls,
35                   .domain.domain == 'login.microsoftonline.com'
36                   and (
37                     strings.ilike(.query_params,
38                                   '*offline_access*',
39                                   '*.readwrite*',
40                                   '*.read*',
41                                   '*ctx=*',
42                                   '*prompt=none*'
43                     )
44                     or (
45                       strings.icontains(.path, '/common/reprocess')
46                       and strings.icontains(.query_params, 'ctx=')
47                       and strings.icontains(.query_params, 'sessionId=')
48                     )
49                   )
50               )
51           )
52    )
53    or any(attachments,
54           (
55             .file_type == "ics"
56             or .file_extension == "ics"
57             or .content_type in ("application/ics", "text/calendar")
58           )
59           //
60           // This rule makes use of a beta feature and is subject to change without notice
61           // using the beta feature in custom rules is not suggested until it has been formally released
62           //
63           and any(beta.file.parse_ics(.).events,
64                   any(.links,
65                       .href_url.domain.domain == 'login.microsoftonline.com'
66                       and (
67                         strings.ilike(.href_url.query_params,
68                                       '*offline_access*',
69                                       '*.readwrite*',
70                                       '*.read*',
71                                       '*ctx=*',
72                                       '*prompt=none*'
73                         )
74                         or (
75                           strings.icontains(.href_url.path, '/common/reprocess')
76                           and strings.icontains(.href_url.query_params, 'ctx=')
77                           and strings.icontains(.href_url.query_params,
78                                                 'sessionId='
79                           )
80                         )
81                       )
82                   )
83           )
84    )
85  )  
86attack_types:
87  - "Credential Phishing"
88detection_methods:
89  - "URL analysis"
90id: "13a8c430-3e62-5c8f-86b5-3722599bead4"
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