Flagsmith/flagsmith

Insufficient validation in ` /api/v1/projects/{project_pk}/features/{feature_pk}/mv-options/`

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#6,615 opened on Jan 28, 2026

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Description

Sentry Issue: FLAGSMITH-API-5GZ

KeyError: 'default_percentage_allocation'
(9 additional frame(s) were not displayed)
...
  File "features/multivariate/views.py", line 89, in create
    return super().create(request, *args, **kwargs)
  File "features/multivariate/serializers.py", line 68, in validate
    total_sibling_percentage_allocation + attrs["default_percentage_allocation"]

Contributor guide

Research direction
Inspect the validation logic in `features/multivariate/serializers.py` line 68 and the create method in `features/multivariate/views.py` line 89 to fix the KeyError for 'default percentage allocation'.
Tech stack
python
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GitPython
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75