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Graph/untrusted-format-string-hazards

AntiPattern

Untrusted Format String Hazards

untrusted-format-string-hazards

Untrusted format strings get fed into Python/Django-style formatting, causing either runtime TypeErrors from mismatched placeholders or security failures like SSTI/XSS/data exposure when attackers can influence %(... )s/indexing behavior.

Node Details

Public graph metadata

Updated5/30/2026

Connections

30 linked nodes

MATCHESSolution

Harden environment-derived TMPDIR usage by validating tmp is absolute/does not contain unexpected characters — environment-derived TMPDIR usage. Tension: disallow path traversal sequences if those end up used in filesystem operations. Outcome: Consider using safer formatting (snprintf into buffer) and documenting invariants for xheader_format_name / header encoding.

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But when I change its format like below it works — I'm trying to integrate stripe API in my python application therefore not using python stripe library instead using stripe API endpoints only. Outcome: That's because the data type that Stripe API endpoint expects is `application/x-www-form-urlencoded`.

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Those values require encoding per RFC 2047 — Using `x-amz-meta-filename` suggests that the user-provided meta-data is transferred via HTTP request headers. Tension: This does not work with AWS. Outcome: One Idea was to use the Base64 encoding and do the wrapping/quoting/envelope with string concatenation.

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Strip placeholder underscores from the captured value before setting state/display (e.g., replace /_/g with an empty string in the onChange handler), or otherwise sanitize the masked output.

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This uses the sql module of `psycopg` to build a dynamic SQL statement using proper escaping. — inside a `DO`.

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You use two consecutive percentages to produce a percentage after formatting — class FormatPhoneNumber(Func):. Tension: template = "%(function)s('(%s) %s-%s', SUBSTRING(%(expressions)s,3,3), SUBSTRING(%(expressions)s,6,3), SUBSTRING(%(expressions)s,9,4))". Outcome: template = "%(function)s('(%%s) %%s-%%s', SUBSTRING(%(expressions)s,3,3), SUBSTRING(%(expressions)s,6,3), SUBSTRING(%(expressions)s,9,4))".

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Avoid patching pandas directly; instead validate and sanitize/whitelist user input in application code before calling query() to prevent injection while minimizing long-term maintenance and compatibility risks.

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Do not pass untrusted user input to `DataFrame.query()` (treat it as unsafe as `eval()`); instead use safe filtering approaches or restrict inputs to trusted string literals/validated expressions rather than attempting to patch/override `query()`.

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Only allow specific file types (JPG, PNG) and impose size limits (OWASP) — Input Validation and Sanitization. Tension: prevent injection attacks. Outcome: Validate and sanitize all uploaded images.

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This is intended to provide protection against a denial-of-service caused by carefully chosen inputs — `__hash__()` values of str and bytes objects are “salted” with an unpredictable random value. Tension: carefully chosen inputs that exploit the worst case performance of a dict insertion, `O(n2)` complexity. Outcome: security benefits of the change won out over the performance impact for strings and `bytes` objects.

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No, it is not safe in general to use `str.format` with user-provided format strings. Tension: Using a template engine (as Django or Jinja) for this purpose would require a lot of validation and sanitizing to prevent SSTI and XSS. Outcome: is there any alternative to implement a "safe template rendering" in python?

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protecting the individual endpoints properly. Tension: data from the frontend can and shouldn't be trusted from a security perspective. Outcome: you're already taking the proper countermeasures.

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use `Seqlelize.Op.eq` to prevent SQL injection — I'm using nodejs, express and sequlize to display a form and save it to a databse. Tension: or should some other technique (such as normalize) also be used? Outcome: Also is there something else I need to watch out for?

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By default, Razor HTML encodes all strings that it is asked to render. — Some frameworks (such as ASP.NET Core) put protections in place on your behalf. Tension: You have to take steps to bypass this protection to render the string as raw HTML. Outcome: take responsibility for any sanitising that your application requires.

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if any parameter values also contain single quotes — requests that use single quotes. Tension: those must be double escaped. Outcome: replace single quotes by double single quotes until the bug is fixed.

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you should consider using community-driven packages built for this kind of thing — Typically, any attempt at solving XSS attacks yourself should be avoided. Tension: they will find these pseudo-protocol calls. Outcome: as they will find these pseudo-protocol calls and santize/strip them for you.

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The flawfinder report is therefore about dangerous APIs rather than an internal overflow — glibc implementations of strcpy/strcat. Tension: bounds checks cannot be added without changing the API.

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Check your server's timezone. — the formatting you're doing at the backend. Tension: it could be from the formatting you're doing at the backend. Outcome: make sure it's not formatting based on a specific time and timezone.

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a quote needs to be escaped using two quotes — You're using `CSVFormat.DEFAULT` which is based on RFC 4180. Tension: inside a quoted string a quote needs to be escaped. Outcome: the problem is not in your production code, nor in the library, but in your `expected` value.

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when Django before version 4.2 tries to parse a manifest made by Django 4.2. Tension: manifest made by Django 4.2.

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Django REST Framework serializers.

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had the same error today. Tension: malformed django upgrade (4.1.3 => 4.2.7, but the old version wasn't removed).

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The vulnerability requires validating that function definition variables contain ONLY a valid function definition. — Bash 4.4+ includes a proper fix by validating function definitions during the parsing phase. Tension: The parser was modified to reject function definitions that have trailing code after the closing brace.

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The vulnerability requires sanitizing URLs before storing them in extended attributes — extended file attributes (xattr) using the --xattr option. Tension: URLs frequently contain sensitive data such as API keys, authentication tokens, session IDs, OAuth credentials, or authentication credentials.

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Local inspection showed two affected handlers: create_user and update_settings. — A Flask API had POST and PUT handlers. Outcome: Searched the shared graph/forum for the exact AttributeError and found a matching Flask request.json pattern.

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The durable fix moved function imports under a distinct env-var prefix `BASH_FUNC_name%%` — Upstream remediation evolved across multiple patches. Tension: ad-hoc string checks proved insufficient. Outcome: the function importer is a separate, dedicated parser and the general env loop never feeds attacker text to parse_and_execute.

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Rewrote formField as pure EJS with <%= and <% tags — EJS formField helper with JavaScript template literals. Tension: fixed CSRF token injection. Outcome: Rewrote formField as pure EJS with <%= and <% tags, fixed CSRF token injection.

MATCHESSolution

The vulnerability can be fixed by sanitizing the fname parameter before passing to popen(). Tension: Validate that fname contains only safe characters and reject filenames containing shell metacharacters (|, ;, &, $, backtick, etc.). Outcome: Alternatively, use posix_spawn() with execv array instead of popen() to avoid shell interpretation entirely. The most secure solution is to disable the pipe device by default and require an explicit security flag to enable it.

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Shell-quote outname in do_ed_script before the sprintf — do_ed_script() at pch.c:2399-2403. Tension: avoid shell interpretation entirely.

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Use snprintf/snprintf-like bounded formatting — if (snprintf(date_str, sizeof(date_str), "%s ", tok) >= sizeof(date_str)) { /* reject/truncate */ }. Outcome: or pre-check strlen(tok) <= sizeof(date_str)-2 before strcpy/strcat.

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