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Default ruleset for Flask, curated by Semgrep.

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Rules (69)

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python.flask.security.injection.ssrf-requests.ssrf-requests

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Data from request object is passed to a new server-side request. This could lead to a server-side request forgery (SSRF). To mitigate, ensure that schemes and hosts are validated against an allowlist, do not forward the response to the user, and ensure proper authentication and transport-layer security in the proxied request.

python.django.security.injection.command.subprocess-injection.subprocess-injection

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Detected user input entering a `subprocess` call unsafely. This could result in a command injection vulnerability. An attacker could use this vulnerability to execute arbitrary commands on the host, which allows them to download malware, scan sensitive data, or run any command they wish on the server. Do not let users choose the command to run. In general, prefer to use Python API versions of system commands. If you must use subprocess, use a dictionary to allowlist a set of commands.

python.flask.security.injection.csv-writer-injection.csv-writer-injection

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Detected user input into a generated CSV file using the built-in `csv` module. If user data is used to generate the data in this file, it is possible that an attacker could inject a formula when the CSV is imported into a spreadsheet application that runs an attacker script, which could steal data from the importing user or, at worst, install malware on the user's computer. `defusedcsv` is a drop-in replacement with the same API that will attempt to mitigate formula injection attempts. You can use `defusedcsv` instead of `csv` to safely generate CSVs.

python.flask.security.injection.nan-injection.nan-injection

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Found user input going directly into typecast for bool(), float(), or complex(). This allows an attacker to inject Python's not-a-number (NaN) into the typecast. This results in undefind behavior, particularly when doing comparisons. Either cast to a different type, or add a guard checking for all capitalizations of the string 'nan'.

python.flask.security.injection.raw-html-concat.raw-html-format

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Detected user input flowing into a manually constructed HTML string. You may be accidentally bypassing secure methods of rendering HTML by manually constructing HTML and this could create a cross-site scripting vulnerability, which could let attackers steal sensitive user data. To be sure this is safe, check that the HTML is rendered safely. Otherwise, use templates (`flask.render_template`) which will safely render HTML instead.

python.flask.security.injection.subprocess-injection.subprocess-injection

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Detected user input entering a `subprocess` call unsafely. This could result in a command injection vulnerability. An attacker could use this vulnerability to execute arbitrary commands on the host, which allows them to download malware, scan sensitive data, or run any command they wish on the server. Do not let users choose the command to run. In general, prefer to use Python API versions of system commands. If you must use subprocess, use a dictionary to allowlist a set of commands.

python.flask.security.injection.tainted-sql-string.tainted-sql-string

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Detected user input used to manually construct a SQL string. This is usually bad practice because manual construction could accidentally result in a SQL injection. An attacker could use a SQL injection to steal or modify contents of the database. Instead, use a parameterized query which is available by default in most database engines. Alternatively, consider using an object-relational mapper (ORM) such as SQLAlchemy which will protect your queries.

python.flask.security.injection.tainted-url-host.tainted-url-host

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User data flows into the host portion of this manually-constructed URL. This could allow an attacker to send data to their own server, potentially exposing sensitive data such as cookies or authorization information sent with this request. They could also probe internal servers or other resources that the server runnig this code can access. (This is called server-side request forgery, or SSRF.) Do not allow arbitrary hosts. Instead, create an allowlist for approved hosts hardcode the correct host.